'\" te
.\" Copyright (c) 1982-2007 AT&T Knowledge Ventures
.\" To view license terms, see http://www.opensource.org/licenses/cpl1.0.txt
.\" Portions Copyright (c) 2009, 2012, Oracle and/or its affiliates. All rights reserved.
.TH ksh 1 "4 Jan 2012" "SunOS 5.11" "User Commands"
.SH NAME
ksh, ksh93, rksh \- Korn Shell, a standard and restricted command and programming language
.SH SYNOPSIS
.LP
.nf
\fBksh\fR [\fB\(+-abcefhikmnoprstuvxBCD\fR] [\fB-R\fR \fIfile\fR] [ \fB\(+-o\fR \fIoption\fR] ...
       [-] [\fIarg\fR ...]
.fi

.LP
.nf
\fBrksh\fR [\fB\(+-abcefhikmnoprstuvxBCD\fR] [\fB-R\fR \fIfile\fR] [\fB\(+-o\fR \fIoption\fR] ...
       [-] [\fIarg\fR ...]
.fi

.SH DESCRIPTION
.sp
.LP
\fBksh\fR is a command and programming language that executes commands read from a terminal or a file. \fBrksh\fR is a restricted version of the command interpreter \fBksh\fR. \fBrksh\fR is used to set up login names and execution environments whose capabilities are more controlled than those of the standard shell.
.sp
.LP
See \fBInvocation\fR for the meaning of arguments to the shell.
.SS "Definitions"
.sp
.LP
A \fImetacharacter\fR is defined as one of the following characters:
.sp
.in +2
.nf
; & ( ) | < > NEWLINE SPACE TAB
.fi
.in -2
.sp

.sp
.LP
A \fIblank\fR is a \fBTAB\fR or a \fBSPACE\fR. 
.sp
.LP
An \fIidentifier\fR is a sequence of letters, digits, or underscores starting with a letter or underscore. Identifiers are used as components of \fIvariable names\fR. 
.sp
.LP
A \fIvname\fR is a sequence of one or more identifiers separated by a period (\fB\&.\fR) and optionally preceded by a period (\fB\&.\fR). \fIvnames\fR are used as function and variable names. 
.sp
.LP
A \fIword\fR is a sequence of \fIcharacters\fR from the character set defined by the current locale, excluding non-quoted \fImetacharacters\fR.
.sp
.LP
A \fIcommand\fR is a sequence of characters in the syntax of the shell language. The shell reads each command and carries out the desired action either directly or by invoking separate utilities. A built-in command is a command that is carried out by the shell itself without creating a separate process. Some commands are built-in purely for convenience and are not documented in this manual page. Built-ins that cause side effects in the shell environment and built-ins that are found before performing a path search (see \fBExecution\fR) are documented in this manual page. For historical reasons, some of these built-ins behave differently than other built-ins and are called special built-ins.
.SS "Commands"
.sp
.LP
A \fIsimple-command\fR is a list of variable assignments (see \fBVariable Assignments\fR) or a sequence of \fIblank\fR-separated words which can be preceded by a list of variable assignments. See the \fBEnvironment\fR section of this manual page.
.sp
.LP
The first word specifies the name of the command to be executed. Except as specified in this section, the remaining words are passed as arguments to the invoked command. The command name is passed as argument 0. See \fBexec\fR(2). The \fIvalue\fR of a simple-command is its exit status. If it terminates normally, its value is \fB0\fR-\fB255\fR. If it terminates abnormally, its value is \fB256+\fR\fIsignum\fR. The name of the signal corresponding to the exit status can be obtained by way of the \fB-l\fR option of the kill built-in utility. 
.sp
.LP
A \fIpipeline\fR is a sequence of one or more commands separated by \fB|\fR. The standard output of each command but the last is connected by a \fBpipe\fR(2) to the standard input of the next command. Each command, except possibly the last, is run as a separate process. The shell waits for the last command to terminate. The exit status of a pipeline is the exit status of the last command unless the \fBpipefail\fR option is enabled. Each pipeline can be preceded by the reserved word\fB!\fR. This causes the exit status of the pipeline to become \fB0\fR if the exit status of the last command is \fBnon-zero\fR, and \fB1\fR if the exit status of the last command is \fB0\fR.
.sp
.LP
A \fIlist\fR is a sequence of one or more pipelines separated by \fB;, &, |&, &&, or |\fR, and optionally terminated by \fB;, &,\fR or \fB|&\fR. Of these five symbols, \fB;, &\fR, and \fB|&\fR have equal precedence, which is lower than that of \fB&&\fR and \fB||\fR. The symbols \fB&&\fR and \fB||\fR also have equal precedence. 
.sp
.LP
A semicolon (\fB;\fR) causes sequential execution of the preceding pipeline. An ampersand (\fB&\fR) causes asynchronous execution of the preceding pipeline, that is, the shell does \fInot\fR wait for that pipeline to finish. The symbol \fB|&\fR causes asynchronous execution of the preceding pipeline with a two-way pipe established to the parent shell. The standard input and output of the spawned pipeline can be written to and read from by the parent shell by applying the redirection operators \fB<&\fR and \fB>&\fR with \fBarg p\fR to commands and by using \fB-p\fR option of the built-in commands \fBread\fR and \fBprint\fR. The symbol \fB&&\fR (\fB||\fR) causes the \fIlist\fR following it to be executed only if the preceding pipeline returns a zero (\fBnon-zero\fR) value. One or more NEWLINEs can appear in a \fIlist\fR instead of a semicolon, to delimit a command. The first \fIitem\fR of the first \fIpipeline\fR of a \fIlist\fR that is a simple command not beginning with a redirection, and not occurring within a \fBwhile\fR, \fBuntil\fR, or \fBif\fR \fIlist\fR , can be preceded by a semicolon. This semicolon is ignored unless the \fBshowme\fR option is enabled as described with the \fBset\fR built-in.
.sp
.LP
A \fIcommand\fR is either a simple-command or one of commands in the following list. Unless otherwise stated, the value returned by a command is that of the last simple-command executed in the command.
.sp
.ne 2
.mk
.na
\fB\fBfor\fR \fIvname\fR \fB[ in\fR \fIword\fR \fB\&... ] ;do\fR \fIlist\fR \fB;done\fR\fR
.ad
.sp .6
.RS 4n
Each time a \fBfor\fR command is executed, \fIvname\fR is set to the next \fIword\fR taken from the \fBin\fR \fIword\fR list. If \fBin\fR \fIword ...\fR is omitted, the \fBfor\fR command executes the \fBdo\fR \fIlist\fR once for each positional parameter that is set starting from 1. Execution ends when there are no more words in the list. See \fBParameter Expansion\fR. 
.RE

.sp
.ne 2
.mk
.na
\fB\fB(( [\fR\fIexpr1\fR\fB] ; [\fR\fIexpr2\fR] ; [\fIexpr3\fR\fB] )) ;do\fR \fIlist\fR \fB;done\fR\fR
.ad
.sp .6
.RS 4n
The arithmetic expression \fIexpr1\fR is evaluated first. The arithmetic expression \fIexpr2\fR is repeatedly evaluated until it evaluates to \fBzero\fR and when \fBnon-zero\fR, \fIlist\fR is executed and the arithmetic expression \fIexpr3\fR evaluated. If any expression is omitted, then it behaves as if it evaluated to \fB1\fR. See \fBArithmetic Evaluation\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBselect\fR \fIvname\fR [ in \fIword\fR \fB\&... ] ;do\fR \fIlist\fR \fB;done\fR\fR
.ad
.sp .6
.RS 4n
A \fBselect\fR command prints on standard error (file descriptor 2) the set of \fIwords\fR, each preceded by a number. If \fBin\fR \fIword...\fR is omitted, the positional parameters starting from \fB1\fR are used instead. See \fBParameter Expansion\fR. The \fBPS3\fR prompt is printed and a line is read from the standard input. If this line consists of the number of one of the listed \fIword\fRs, then the value of the variable \fIvname\fR is set to the \fIword\fR corresponding to this number. If this line is empty, the selection list is printed again. Otherwise the value of the variable \fIvname\fR is set to \fBnull\fR. The contents of the line read from standard input is saved in the variable \fBREPLY\fR. The \fIlist\fR is executed for each selection until a break or \fBEOF\fR is encountered. If the \fBREPLY\fR variable is set to \fBnull\fR by the execution of \fIlist\fR, the selection list is printed before displaying the \fBPS3\fR prompt for the next selection.
.RE

.sp
.ne 2
.mk
.na
\fB\fBcase\fR \fIword\fR \fBin [ [(]\fR \fIpattern\fR \fB[ |\fR \fIpattern\fR \fB] ... )\fR \fIlist\fR \fB;; ] ... esac\fR\fR
.ad
.sp .6
.RS 4n
A \fBcase\fR command executes the \fIlist\fR associated with the first \fIpattern\fR that matches \fIword\fR. The form of the patterns is the same as that used for file name generation. See \fBFile Name Generation\fR. 
.sp
The \fB;;\fR operator causes execution of \fBcase\fR to terminate. If \fB;&\fR is used in place of \fB;;\fR the next subsequent list, if any, is executed.
.RE

.sp
.ne 2
.mk
.na
\fB\fBif\fR \fIlist\fR \fB;then\fR \fIlist\fR \fB[ ;elif\fR \fIlist\fR \fB;then\fR \fIlist\fR ] \fB\&... [ ;else\fR \fIlist\fR \fB]\fR \fB;fi\fR\fR
.ad
.sp .6
.RS 4n
The \fIlist\fR following \fBif\fR is executed and, if it returns a \fBzero\fR exit status, the \fIlist\fR following the first \fBthen\fR is executed. Otherwise, the \fIlist\fR following \fBelif\fR is executed, and, if its value is \fBzero\fR, the \fIlist\fR following the next \fBthen\fR is executed. Failing each successive \fBelif\fR \fIlist\fR, the \fBelse\fR \fIlist\fR is executed. If the \fBif\fR \fIlist\fR has \fBnon-zero\fR exit status and there is no \fBelse\fR \fIlist\fR, then the \fBif\fR command returns a \fBzero\fR exit status.
.RE

.sp
.ne 2
.mk
.na
\fB\fBwhile\fR \fIlist\fR \fB;do\fR \fIlist\fR \fB;done\fR\fR
.ad
.br
.na
\fBuntil \fIlist\fR \fB;do\fR \fIlist\fR \fB;done\fR\fR
.ad
.sp .6
.RS 4n
A \fBwhile\fR command repeatedly executes the while \fIlist\fR and, if the exit status of the last command in the list is zero, executes the \fBdo\fR \fIlist\fR, otherwise the loop terminates. If no commands in the \fBdo\fR \fIlist\fR are executed, then the \fBwhile\fR command returns a \fBzero\fR exit status, \fBuntil\fR can be used in place of \fBwhile\fR to negate the loop termination test.
.RE

.sp
.ne 2
.mk
.na
\fB\fB((\fR\fIexpression\fR\fB))\fR\fR
.ad
.sp .6
.RS 4n
The \fIexpression\fR is evaluated using the rules for arithmetic evaluation described in this manual page. If the value of the arithmetic expression is \fBnon-zero\fR, the exit status is \fB0\fR. Otherwise the exit status is \fB1\fR. 
.RE

.sp
.ne 2
.mk
.na
\fB\fB(\fR\fIlist\fR\fB;)\fR\fR
.ad
.sp .6
.RS 4n
Execute list in a separate environment. If two adjacent open parentheses are needed for nesting, a SPACE must be inserted to avoid evaluation as an arithmetic command as described in this section.
.sp
\fIlist\fR is simply executed. Unlike the metacharacters, \fB(\fR and \fB)\fR, \fB{\fR and \fB}\fR are \fIreserved words\fR and must occur at the beginning of a line or after a \fB;\fR to be recognized. 
.RE

.sp
.ne 2
.mk
.na
\fB\fB[[\fR \fIexpression\fR \fB]]\fR\fR
.ad
.sp .6
.RS 4n
Evaluates \fIexpression\fR and returns a \fBzero\fR exit status when \fIexpression\fR is true. See \fBConditional Expressions\fR for a description of \fIexpression\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBfunction\fR \fIvarname\fR \fB{\fR \fIlist\fR \fB;}\fR\fR
.ad
.br
.na
\fB\fIvarname\fR \fB() {\fR \fIlist\fR \fB;}\fR\fR
.ad
.sp .6
.RS 4n
Define a function which is referenced by \fIvarname\fR. A function whose \fIvarname\fR contains a \fB\&.\fR is called a discipline function and the portion of the \fIvarname\fR preceding the last \fB\&.\fR must refer to an existing variable. 
.sp
The body of the function is the \fIlist\fR of commands between \fB{\fR and \fB}\fR. A function defined with the function \fIvarname\fR syntax can also be used as an argument to the \fB\&.\fR special built-in command to get the equivalent behavior as if the \fIvarname\fR\fB()\fR syntax were used to define it. See \fBFunctions\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBtime [\fR \fIpipeline\fR \fB]\fR\fR
.ad
.sp .6
.RS 4n
If \fIpipeline\fR is omitted, the user and system time for the current shell and completed child processes is printed on standard error. Otherwise, \fIpipeline\fR is executed and the elapsed time as well as the user and system time are printed on standard error. The \fBTIMEFORMAT\fR variable can be set to a format string that specifies how the timing information should be displayed. See \fBShell Variables\fR for a description of the \fBTIMEFORMAT\fR variable. 
.RE

.sp
.LP
The following reserved words are recognized as reserved only when they are the first word of a command and are not quoted: 
.br
.in +2
\fBcase\fR
.in -2
.br
.in +2
\fBdo\fR
.in -2
.br
.in +2
\fBdone\fR
.in -2
.br
.in +2
\fBelse\fR
.in -2
.br
.in +2
\fBelif\fR
.in -2
.br
.in +2
\fBesac\fR
.in -2
.br
.in +2
\fBfor\fR
.in -2
.br
.in +2
\fBfi\fR
.in -2
.br
.in +2
\fBfunction\fR
.in -2
.br
.in +2
\fBif\fR
.in -2
.br
.in +2
\fBselect\fR
.in -2
.br
.in +2
\fBthen\fR
.in -2
.br
.in +2
\fBtime\fR
.in -2
.br
.in +2
\fBuntil\fR
.in -2
.br
.in +2
\fBwhile\fR
.in -2
.br
.in +2
\fB{ }\fR
.in -2
.br
.in +2
\fB[[ ]]\fR
.in -2
.br
.in +2
\fB!\fR
.in -2
.SS "Variable Assignments"
.sp
.LP
One or more variable assignments can start a simple command or can be arguments to the \fBtypeset\fR, \fBexport\fR, or \fBreadonly\fR special built-in commands. The syntax for an \fIassignment\fR is of the form:
.sp
.ne 2
.mk
.na
\fB\fIvarname\fR\fB=\fR\fIword\fR\fR
.ad
.br
.na
\fB\fIvarname\fR\fB[\fR\fIword\fR\fB]=\fR\fIword\fR\fR
.ad
.sp .6
.RS 4n
No space is permitted between \fIvarname\fR and the \fB=\fR or between \fB=\fR and \fIword\fR. 
.RE

.sp
.ne 2
.mk
.na
\fB\fIvarname\fR\fB=(\fR\fIassignlist\fR\fB)\fR\fR
.ad
.sp .6
.RS 4n
No space is permitted between \fIvarname\fR and the \fB=\fR. An \fIassignlist\fR can be one of the following:
.sp
.ne 2
.mk
.na
\fB\fIword ...\fR\fR
.ad
.sp .6
.RS 4n
Indexed array assignment.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIword\fR\fB]=\fR\fIword ...\fR\fR
.ad
.sp .6
.RS 4n
Associative array assignment. If prefixed by \fBtypeset\fR \fB-a\fR, creates an indexed array instead.
.RE

.sp
.ne 2
.mk
.na
\fB\fIassignment ...\fR\fR
.ad
.sp .6
.RS 4n
Compound variable assignment. This creates a compound variable \fIvarname\fR with sub-variables of the form \fIvarname.name\fR, where \fIname\fR is the name portion of assignment. The value of \fIvarname\fR contains all the assignment elements. Additional assignments made to sub-variables of \fIvarname\fR are also displayed as part of the value of \fIvarname\fR. If no \fIassignment\fRs are specified, \fIvarname\fR is a compound variable allowing subsequence child elements to be defined.
.RE

.sp
.ne 2
.mk
.na
\fB\fBtypeset [\fR\fIoptions\fR] \fIassignment\fR \fB\&...\fR\fR
.ad
.sp .6
.RS 4n
Nested variable assignment. Multiple assignments can be specified by separating each of them with a \fB;\fR. The previous value is unset before the assignment.
.RE

In addition, a \fB+=\fR can be used in place of the \fB=\fR to signify adding to or appending to the previous value. When \fB+=\fR is applied to an arithmetic type, \fIword\fR is evaluated as an arithmetic expression and added to the current value. When applied to a string variable, the value defined by \fIword\fR is appended to the value. For compound assignments, the previous value is not unset and the new values are appended to the current ones provided that the types are compatible. 
.RE

.SS "Comments"
.sp
.LP
A word beginning with \fB#\fR causes that word and all the following characters up to a NEWLINE to be commented, or ignored.
.SS "Aliasing"
.sp
.LP
The first word of each command is replaced by the text of an alias if an alias for this word has been defined. An alias name consists of any number of characters excluding metacharacters, quoting characters, file expansion characters, parameter expansion characters, command substitution characters, and \fB=\fR. The replacement string can contain any valid shell script including the metacharacters listed in the \fBCommands\fR section. The first word of each command in the replaced text, other than any that are in the process of being replaced, are tested for aliases. If the last character of the alias value is a BLANK then the word following the alias is also checked for alias substitution. 
.sp
.LP
Aliases can be used to redefine built-in commands but cannot be used to redefine the reserved words listed in the \fBCommands\fR section. Aliases can be created and listed with the alias command and can be removed with the \fBunalias\fR command.
.sp
.LP
Aliasing is performed when scripts are read, not while they are executed. For an alias to take effect, the \fBalias\fR definition command has to be executed before the command which references the alias is read. The following aliases are compiled into the shell but can be unset or redefined:
.sp
.in +2
.nf
autoload='typeset -fu'
command='command '
fc=hist
float='typeset -lE'
functions='typeset -f'
hash='alias -t --'
history='hist -l'
integer='typeset -li'
nameref='typeset -n'
nohup='nohup '
r='hist -s'
redirect='command exec'
source='command .'
stop='kill -s STOP'
suspend='kill -s STOP $$'
times='{ { time;} 2>&1;}'
type='whence -v'
.fi
.in -2
.sp

.SS "Tilde Substitution"
.sp
.LP
After alias substitution is performed, each word is checked to see if it begins with an unquoted tilde (\fB~\fR). For tilde substitution, \fIword\fR also refers to the \fIword\fR portion of parameter expansion. See \fBParameter Expansion\fR. 
.sp
.LP
If it does, the word up to a \fB/\fR is checked to see if it matches a user name in the password database. If a match is found, the \fB~\fR and the matched login name are replaced by the login directory of the matched user. If no match is found, the original text is left unchanged. A \fB~\fR by itself, or in front of a \fB/\fR, is replaced by \fB$HOME\fR. A \fB~\fR followed by a \fB+\fR or \fB-\fR is replaced by the value of \fB$PWD\fR and \fB$OLDPWD\fR respectively.
.sp
.LP
In addition, when expanding a \fIvariable assignment\fR, tilde substitution is attempted when the value of the assignment begins with a \fB~\fR, and when a \fB~\fR appears after a colon (\fB:\fR). The \fB:\fR also terminates a \fB~\fR login name.
.SS "Command Substitution"
.sp
.LP
The standard output from a command enclosed in parentheses preceded by a dollar sign (\fB$\fR) or a pair of grave accents (\fB``\fR) can be used as part or all of a word. Trailing NEWLINEs are removed. In the second (obsolete) form, the string between the quotes is processed for special quoting characters before the command is executed. See \fBQuoting\fR. 
.sp
.LP
The command substitution \fB$(cat file)\fR can be replaced by the equivalent but faster \fB$(<file)\fR. The command substitution \fB$(\fR\fIn\fR\fB<#)\fR expands to the current byte offset for file descriptor \fIn\fR.
.SS "Arithmetic Substitution"
.sp
.LP
An arithmetic expression enclosed in double parentheses preceded by a dollar sign ( \fB$((\fR\fIarithmetic_expression\fR\fB))\fR) is replaced by the value of the arithmetic expression within the double parentheses.
.SS "Process Substitution"
.sp
.LP
Process substitution is only available on versions of the UNIX operating system that support the \fB/dev/fd\fR directory for naming open files. 
.sp
.LP
Each command argument of the form \fB<(\fR\fIlist\fR\fB)\fR or \fB>(\fR\fIlist\fR\fB)\fR runs process \fIlist\fR asynchronously connected to some file in \fB/dev/fd\fR. The name of this file becomes the argument to the command. If the form with \fB>\fR is selected then writing on this file provides input for \fIlist\fR. If \fB<\fR is used, then the file passed as an argument contains the output of the \fIlist\fR process. 
.sp
.LP
For example,
.sp
.in +2
.nf
paste <(cut -f1 \fIfile1\fR) <(cut -f3 \fIfile2\fR) | tee \e
     >(\fIprocess1\fR) >(\fIprocess2\fR)
.fi
.in -2
.sp

.sp
.LP
\fBcut\fRs fields 1 and 3 from the files \fIfile1\fR and \fIfile2\fR respectively, \fBpaste\fRs the results together, and sends it to the processes \fIprocess1\fR and \fIprocess2\fR. It also displays the results to the standard output. The file, which is passed as an argument to the command, is a UNIX \fBpipe\fR(2). Programs that expect to \fBlseek\fR(2) on the file do not work. 
.SS "Parameter Expansion"
.sp
.LP
A parameter is a variable, one or more digits, or any of the characters \fB*\fR, \fB@\fR, \fB#\fR, \fB?\fR, \fB-\fR, \fB$\fR, and \fB!\fR. A variable is denoted by a \fIvname\fR. To create a variable whose \fIvname\fR contains a \fB\&.\fR, a variable whose \fBvname\fR consists of everything before the last . must already exist. A variable has a value and zero or more attributes. Variables can be assigned values and attributes by using the \fBtypeset\fR special built-in command. The attributes supported by the shell are described later with the \fBtypeset\fR special built-in command. Exported variables pass values and attributes to the environment. 
.sp
.LP
The shell supports both indexed and associative arrays. An element of an array variable is referenced by a subscript. A subscript for an indexed array is denoted by an arithmetic expression, (see \fBArithmetic Evaluation\fR), between a \fB[\fR and a \fB]\fR. Use \fBset -A\fR \fIvname value ...\fR to assign values to an indexed array. The value of all subscripts must be in the range of \fB0\fR through \fB1,048,575\fR. Indexed arrays do not need to be declared. Any reference to a variable with a valid subscript is legal and an array is created if necessary. 
.sp
.LP
An associative array is created with the \fB-A\fR option to \fBtypeset\fR. A subscript for an associative array is denoted by a string enclosed between \fB[\fR and \fB]\fR. 
.sp
.LP
Referencing any array without a subscript is equivalent to referencing the array with subscript \fB0\fR.
.sp
.LP
The value of a variable can be assigned by:
.sp
.in +2
.nf
\fIvname\fR=\fIvalue\fR [\fIvname\fR=\fIvalue\fR] ...
.fi
.in -2
.sp

.sp
.LP
or
.sp
.in +2
.nf
\fIvname\fR[\fIsubscript\fR]=\fIvalue\fR [\fIvname\fR[\fIsubscript\fR]=\fIvalue\fR] ...
.fi
.in -2
.sp

.sp
.LP
No space is allowed before or after the \fB=\fR. A \fInameref\fR is a variable that is a reference to another variable. A \fInameref\fR is created with the \fB-n\fR attribute of \fBtypeset\fR. The value of the variable at the time of the \fBtypeset\fR command becomes the variable that is referenced whenever the \fInameref\fR variable is used. The name of a \fInameref\fR cannot contain a dot (\fI\&.\fR). When a variable or function name contains a \fB\&.,\fR and the portion of the name up to the first \fB\&.\fR matches the name of a \fInameref\fR, the variable referred to is obtained by replacing the \fInameref\fR portion with the name of the variable referenced by the \fInameref\fR. If a \fInameref\fR is used as the index of a \fBfor\fR loop, a name reference is established for each item in the list. A \fInameref\fR provides a convenient way to refer to the variable inside a function whose name is passed as an argument to a function. For example, if the name of a variable is passed as the first argument to a function, the command
.sp
.in +2
.nf
 typeset -n var=$1
.fi
.in -2
.sp

.sp
.LP
inside the function causes references and assignments to \fIvar\fR to be references and assignments to the variable whose name has been passed to the function. If either of the floating point attributes, \fB-E\fR, or \fB-F\fR, or the integer attribute, \fB-i\fR, is set for \fIvname\fR, then the \fIvalue\fR is subject to arithmetic evaluation as described in this manual page. Positional parameters, parameters denoted by a number, can be assigned values with the \fBset\fR special built-in command. Parameter \fB$0\fR is set from argument zero when the shell is invoked. The character \fB$\fR is used to introduce substitutable parameters.
.sp
.ne 2
.mk
.na
\fB\fB${\fR\fIparameter\fR\fB}\fR\fR
.ad
.sp .6
.RS 4n
The shell reads all the characters from \fB${\fR to the matching \fB}\fR as part of the same word even if it contains braces or metacharacters. The value, if any, of the parameter is substituted. The braces are required when \fIparameter\fR is followed by a letter, digit, or underscore that is not to be interpreted as part of its name, when the variable name contains a \fB\&.\fR, or when a variable is subscripted. If \fIparameter\fR is one or more digits then it is a positional parameter. A positional parameter of more than one digit must be enclosed in braces. If \fIparameter\fR is \fB*\fR or \fB@\fR, then all the positional parameters, starting with \fB$1\fR, are substituted and separated by a field separator character. If an array \fIvname\fR with subscript \fB*\fR or \fB@\fR is used, then the value for each of the elements is substituted, separated by the first character of the value of \fBIFS\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB${#\fR\fIparameter\fR\fB}\fR\fR
.ad
.sp .6
.RS 4n
If \fIparameter\fR is \fB*\fR or \fB@\fR, the number of positional parameters is substituted. Otherwise, the length of the value of the \fIparameter\fR is substituted.
.RE

.sp
.ne 2
.mk
.na
\fB\fB${#\fR\fIvname\fR\fB[*]}\fR\fR
.ad
.br
.na
\fB\fB${#\fR\fIvname\fR\fB[@]}\fR\fR
.ad
.sp .6
.RS 4n
The number of elements in the array \fIvname\fR is substituted.
.RE

.sp
.ne 2
.mk
.na
\fB\fB${!\fR\fIvname\fR\fB}\fR\fR
.ad
.sp .6
.RS 4n
Expands to the name of the variable referred to by \fIvname\fR. This is \fIvname\fR except when \fIvname\fR is a name reference.
.RE

.sp
.ne 2
.mk
.na
\fB\fB${!\fR\fIvname\fR\fB[\fR\fIsubscript\fR\fB]}\fR\fR
.ad
.sp .6
.RS 4n
Expands to name of the subscript unless \fIsubscript\fR is \fB*\fR or \fB@\fR. When \fIsubscript\fR is \fB*\fR, the list of array subscripts for \fIvname\fR is generated. For a variable that is not an array, the value is \fB0\fR if the variable is set. Otherwise it is \fBnull\fR. When \fIsubscript\fR is \fB@\fR, it is the same as \fB$ {\fR\fIvname\fR\fB[\fR\fI*\fR\fB]}\fR, except that when used in double quotes, each array subscript yields a separate argument.
.RE

.sp
.ne 2
.mk
.na
\fB\fB${!\fR\fIprefix\fR\fB*}\fR\fR
.ad
.sp .6
.RS 4n
Expands to the names of the variables whose names begin with \fIprefix\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB${\fR\fIparameter\fR\fB:-\fR\fIword\fR\fB}\fR\fR
.ad
.sp .6
.RS 4n
If \fIparameter\fR is set and is non-null then substitute its value. Otherwise substitute \fIword\fR.
.sp
\fIword\fR is not evaluated unless it is to be used as the substituted string. 
.sp
In the following example, \fBpwd\fR is executed only if \fBd\fR is not set or is NULL:
.sp
.in +2
.nf
print ${d:-$(pwd)}
.fi
.in -2
.sp

If the colon (\fB:\fR ) is omitted from the expression, the shell only checks whether \fIparameter\fR is set or not. 
.RE

.sp
.ne 2
.mk
.na
\fB\fB${\fR\fIparameter\fR\fB:\fR\fIoffset\fR:\fIlength\fR}\fR
.ad
.br
.na
\fB\fB${\fR\fIparameter\fR\fB:\fR\fIoffset\fR\fB}\fR\fR
.ad
.sp .6
.RS 4n
Expands to the portion of the value of \fIparameter\fR starting at the character (counting from \fB0\fR) determined by expanding offset as an arithmetic expression and consisting of the number of characters determined by the arithmetic expression defined by \fIlength\fR. 
.sp
In the second form, the remainder of the value is used. A negative offset counts backwards from the end of \fIparameter\fR.
.sp
One or more BLANKs is required in front of a minus sign to prevent the shell from interpreting the operator as \fB:-\fR. If parameter is \fB*\fR or \fB@\fR, or is an array name indexed by \fB*\fR or \fB@\fR, then \fIoffset\fR and \fIlength\fR refer to the array index and number of elements respectively. A negative \fIoffset\fR is taken relative to one greater than the highest subscript for indexed arrays. The order for associative arrays is unspecified.
.RE

.sp
.ne 2
.mk
.na
\fB\fB${\fR\fIparameter\fR\fB#\fR\fIpattern\fR\fB}\fR\fR
.ad
.br
.na
\fB\fB${\fR\fIparameter\fR\fB##\fR\fIpattern\fR\fB}\fR\fR
.ad
.sp .6
.RS 4n
If the shell \fIpattern\fR matches the beginning of the value of \fIparameter\fR, then the value of this expansion is the value of the \fIparameter\fR with the matched portion deleted. Otherwise the value of this \fIparameter\fR is substituted. In the first form the smallest matching \fIpattern\fR is deleted and in the second form the largest matching \fIpattern\fR is deleted. When \fIparameter\fR is \fB@\fR, \fB*\fR, or an array variable with subscript \fB@\fR or \fB*\fR, the substring operation is applied to each element in turn. 
.RE

.sp
.ne 2
.mk
.na
\fB\fB${\fR\fIparameter\fR\fB%\fR\fIpattern\fR\fB}\fR\fR
.ad
.br
.na
\fB\fB${\fR\fIparameter\fR\fB%%\fR\fIpattern\fR\fB}\fR\fR
.ad
.sp .6
.RS 4n
If the shell \fIpattern\fR matches the end of the value of \fIparameter\fR, then the value of this expansion is the value of the parameter with the matched part deleted. Otherwise substitute the value of \fIparameter\fR. In the first form the smallest matching pattern is deleted, and in the second form the largest matching pattern is deleted. When parameter is \fB@\fR, \fB*\fR, or an array variable with subscript \fB@\fR or \fB*\fR, the substring operation is applied to each element in turn. 
.RE

.sp
.ne 2
.mk
.na
\fB\fB${\fR\fIparameter\fR\fB/\fR\fIpattern\fR\fB/\fR\fIstring\fR\fB}\fR\fR
.ad
.br
.na
\fB\fB${\fR\fIparameter\fR\fB//\fR\fIpattern\fR\fB/\fR\fIstring\fR\fB}\fR\fR
.ad
.br
.na
\fB\fB${\fR\fIparameter\fR\fB/#\fR\fIpattern\fR\fB/\fR\fIstring\fR\fB}\fR\fR
.ad
.br
.na
\fB\fB${\fR\fIparameter\fR\fB/%\fR\fIpattern\fR\fB/\fR\fIstring\fR\fB}\fR\fR
.ad
.sp .6
.RS 4n
Expands \fIparameter\fR and replaces the longest match of \fIpattern\fR with the specified \fIstring\fR. Each occurrence of \fB\e\fR\fIn\fR in \fIstring\fR is replaced by the portion of \fIparameter\fR that matches the \fIn\fR\fBth\fR sub-pattern. 
.sp
When \fIstring\fR is null, the \fIpattern\fR is deleted and the \fB/\fR in front of string can be omitted. When \fIparameter\fR is \fB@\fR, \fB*\fR, or an array variable with subscript \fB@\fR or \fB*\fR, the substitution operation is applied to each element in turn. In this case, the \fIstring\fR portion of \fIword\fR is re-evaluated for each element.
.sp
In the first form, only the first occurrence of \fIpattern\fR is replaced. 
.sp
In the second form, each match for \fIpattern\fR is replaced by the specified \fIstring\fR. 
.sp
The third form restricts the pattern match to the beginning of the \fIstring\fR. 
.sp
The fourth form restricts the pattern match to the end of the \fIstring\fR. 
.RE

.sp
.LP
The following parameters are automatically set by the shell:
.sp
.ne 2
.mk
.na
\fB\fB#\fR\fR
.ad
.RS 19n
.rt  
The number of positional parameters in decimal.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-\fR\fR
.ad
.RS 19n
.rt  
Options supplied to the shell on invocation or by the \fBset\fR command.
.RE

.sp
.ne 2
.mk
.na
\fB\fB?\fR\fR
.ad
.RS 19n
.rt  
The decimal value returned by the last executed command.
.RE

.sp
.ne 2
.mk
.na
\fB\fB$\fR\fR
.ad
.RS 19n
.rt  
The process number of this shell.
.RE

.sp
.ne 2
.mk
.na
\fB\fB_\fR\fR
.ad
.RS 19n
.rt  
Initially, the value of \fB_\fR is the absolute pathname of the shell or script being executed as passed in the environment. It is subsequently assigned the last argument of the previous command. 
.sp
This parameter is not set for commands which are asynchronous. This parameter is also used to hold the name of the matching \fBMAIL\fR file when checking for mail.
.RE

.sp
.ne 2
.mk
.na
\fB\fB!\fR\fR
.ad
.RS 19n
.rt  
The process number of the last background command invoked or the most recent job put in the background with the \fBbg\fR built-in command.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\&.sh.command\fR\fR
.ad
.RS 19n
.rt  
When processing a \fBDEBUG\fR trap, this variable contains the current command line that is about to run.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\&.sh.edchar\fR\fR
.ad
.RS 19n
.rt  
This variable contains the value of the keyboard character (or sequence of characters if the first character is an ESC, \fBASCII 033\fR) that has been entered when processing a \fBKEYBD\fR trap. If the value is changed as part of the trap action, then the new value replaces the key (or key sequence) that caused the trap. See the \fBKey Bindings\fR section of this manual page.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\&.sh.edcol\fR\fR
.ad
.RS 19n
.rt  
The character position of the cursor at the time of the most recent \fBKEYBD\fR trap.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\&.sh.edmode\fR\fR
.ad
.RS 19n
.rt  
The value is set to ESC when processing a \fBKEYBD\fR trap while in \fBvi\fR insert mode. Otherwise, \fB\&.sh.edmode\fR is null when processing a \fBKEYBD\fR trap. See the \fBvi Editing Mode\fR section of this manual page.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\&.sh.edtext\fR\fR
.ad
.RS 19n
.rt  
The characters in the input buffer at the time of the most recent \fBKEYBD\fR trap. The value is null when not processing a \fBKEYBD\fR trap.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\&.sh.file\fR\fR
.ad
.RS 19n
.rt  
The pathname of the file than contains the current command.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\&.sh.fun\fR\fR
.ad
.RS 19n
.rt  
The name of the current function that is being executed.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\&.sh.match\fR\fR
.ad
.RS 19n
.rt  
An indexed array which stores the most recent match and sub-pattern matches after conditional pattern matches that match and after variables expansions using the operators \fB#\fR, \fB%\fR, or \fB/\fR. The \fB0\fRth element stores the complete match and the \fIi\fRth element stores the \fIi\fRth sub-match. The \fB\&.sh.match\fR variable is unset when the variable that has expanded is assigned a new value.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\&.sh.name\fR\fR
.ad
.RS 19n
.rt  
Set to the name of the variable at the time that a discipline function is invoked.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\&.sh.subscript\fR\fR
.ad
.RS 19n
.rt  
Set to the name subscript of the variable at the time that a discipline function is invoked.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\&.sh.subshell\fR\fR
.ad
.RS 19n
.rt  
The current depth for sub-shells and command substitution.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\&.sh.value\fR\fR
.ad
.RS 19n
.rt  
Set to the value of the variable at the time that the set or append discipline function is invoked.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\&.sh.version\fR\fR
.ad
.RS 19n
.rt  
Set to a value that identifies the version of this shell.
.RE

.sp
.ne 2
.mk
.na
\fB\fBLINENO\fR\fR
.ad
.RS 19n
.rt  
The current line number within the script or function being executed.
.RE

.sp
.ne 2
.mk
.na
\fB\fBOLDPWD\fR\fR
.ad
.RS 19n
.rt  
The previous working directory set by the \fBcd\fR command.
.RE

.sp
.ne 2
.mk
.na
\fB\fBOPTARG\fR\fR
.ad
.RS 19n
.rt  
The value of the last option argument processed by the \fBgetopts\fR built-in command.
.RE

.sp
.ne 2
.mk
.na
\fB\fBOPTIND\fR\fR
.ad
.RS 19n
.rt  
The index of the last option argument processed by the \fBgetopts\fR built-in command.
.RE

.sp
.ne 2
.mk
.na
\fB\fBPPID\fR\fR
.ad
.RS 19n
.rt  
The process number of the parent of the shell.
.RE

.sp
.ne 2
.mk
.na
\fB\fBPWD\fR\fR
.ad
.RS 19n
.rt  
The present working directory set by the \fBcd\fR command.
.RE

.sp
.ne 2
.mk
.na
\fB\fBRANDOM\fR\fR
.ad
.RS 19n
.rt  
Each time this variable is referenced, a random integer, uniformly distributed between \fB0\fR and \fB32767\fR, is generated. The sequence of random numbers can be initialized by assigning a numeric value to \fBRANDOM\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBREPLY\fR\fR
.ad
.RS 19n
.rt  
This variable is set by the \fBselect\fR statement and by the \fBread\fR built-in command when no arguments are supplied.
.RE

.sp
.ne 2
.mk
.na
\fB\fBSECONDS\fR\fR
.ad
.RS 19n
.rt  
Each time this variable is referenced, the number of seconds since shell invocation is returned. If this variable is assigned a value, then the value returned upon reference is the value that was assigned plus the number of seconds since the assignment.
.RE

.sp
.LP
The following variables are used by the shell:
.sp
.ne 2
.mk
.na
\fB\fBCDPATH\fR\fR
.ad
.RS 14n
.rt  
Defines the search path for the \fBcd\fR command.
.RE

.sp
.ne 2
.mk
.na
\fB\fBCOLUMNS\fR\fR
.ad
.RS 14n
.rt  
Defines the width of the edit window for the shell edit modes and for printing select lists.
.RE

.sp
.ne 2
.mk
.na
\fB\fBEDITOR\fR\fR
.ad
.RS 14n
.rt  
If the \fBVISUAL\fR variable is not set, the value of this variable is checked for the patterns as described with \fBVISUAL\fR and the corresponding editing option is turned on. 
.sp
See the \fBset\fR command in the \fBSpecial Command\fR section of this manual page. 
.RE

.sp
.ne 2
.mk
.na
\fB\fBENV\fR\fR
.ad
.RS 14n
.rt  
Performs parameter expansion, command substitution, and arithmetic substitution on the value to generate the pathname of the script that is executed when the shell is invoked. This file is typically used for alias and function definitions. The default value is \fB$HOME/.kshrc\fR. 
.sp
See the \fBInvocation\fR section of this manual page.
.sp
\fBENV\fR is not set by the shell. 
.RE

.sp
.ne 2
.mk
.na
\fB\fBFCEDIT\fR\fR
.ad
.RS 14n
.rt  
Obsolete name for the default editor name for the \fBhist\fR command. \fBFCEDIT\fR is not used when \fBHISTEDIT\fR is set.
.sp
The shell specifies a default value to \fBFCEDIT\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBFIGNORE\fR\fR
.ad
.RS 14n
.rt  
A pattern that defines the set of file names that is ignored when performing file name matching.
.RE

.sp
.ne 2
.mk
.na
\fB\fBFPATH\fR\fR
.ad
.RS 14n
.rt  
The search path for function definitions. The directories in this path are searched for a file with the same name as the function or command when a function with the \fB-u\fR attribute is referenced and when a command is not found. If an executable file with the name of that command is found, then it is read and executed in the current environment. Unlike \fBPATH\fR, the current directory must be represented explicitly by dot (\fB\&.\fR) rather than by adjacent colon (\fB:\fR) characters or a beginning or ending colon (\fB:\fR).
.RE

.sp
.ne 2
.mk
.na
\fB\fBHISTCMD\fR\fR
.ad
.RS 14n
.rt  
The number of the current command in the history file.
.RE

.sp
.ne 2
.mk
.na
\fB\fBHISTEDIT\fR\fR
.ad
.RS 14n
.rt  
The name for the default editor name for the \fBhist\fR command.
.RE

.sp
.ne 2
.mk
.na
\fB\fBHISTFILE\fR\fR
.ad
.RS 14n
.rt  
If this variable is set when the shell is invoked, the value is the pathname of the file that is used to store the command history. See the \fBCommand Re-entry\fR section of this manual page. 
.RE

.sp
.ne 2
.mk
.na
\fB\fBHISTSIZE\fR\fR
.ad
.RS 14n
.rt  
If this variable is set when the shell is invoked, then the number of previously entered commands that are accessible by this shell is greater than or equal to this number. The default is \fB512\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBHOME\fR\fR
.ad
.RS 14n
.rt  
The default argument (home directory) for the \fBcd\fR command.
.sp
\fBHOME\fR is not set by the shell. \fBHOME\fR is set by \fBlogin\fR(1).
.RE

.sp
.ne 2
.mk
.na
\fB\fBIFS\fR\fR
.ad
.RS 14n
.rt  
Internal field separators, normally SPACE, TAB, and NEWLINE that are used to separate the results of command substitution or parameter expansion and to separate fields with the built-in command read. The first character of the \fBIFS\fR variable is used to separate arguments for the \fB"$*"\fR substitution. See the \fBQuoting\fR section of this manual page. 
.sp
Each single occurrence of an \fBIFS\fR character in the string to be split, that is not in the \fBissspace\fR character class, and any adjacent characters in \fBIFS\fR that are in the \fBissspace\fR character class, delimit a field. One or more characters in IFS that belong to the \fBissspace\fR character class, delimit a field. In addition, if the same \fBissspace\fR character appears consecutively inside \fBIFS\fR, this character is treated as if it were not in the \fBissspace\fR class, so that if \fBIFS\fR consists of two tab characters, then two adjacent tab characters delimit a null field.
.sp
The shell specifies a default value to \fBIFS\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBLANG\fR\fR
.ad
.RS 14n
.rt  
This variable determines the locale category for any category not specifically selected with a variable starting with \fBLC_\fR or \fBLANG\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBLC_ALL\fR\fR
.ad
.RS 14n
.rt  
This variable overrides the value of the \fBLANG\fR variable and any other \fBLC_\fR variable.
.RE

.sp
.ne 2
.mk
.na
\fB\fBLC_COLLATE\fR\fR
.ad
.RS 14n
.rt  
This variable determines the locale category for character collation information.
.RE

.sp
.ne 2
.mk
.na
\fB\fBLC_CTYPE\fR\fR
.ad
.RS 14n
.rt  
This variable determines the locale category for character handling functions. It determines the character classes for pattern matching. See the \fBFile Name Generation\fR section of this manual page.
.RE

.sp
.ne 2
.mk
.na
\fB\fBLC_NUMERIC\fR\fR
.ad
.RS 14n
.rt  
This variable determines the locale category for the decimal point character.
.RE

.sp
.ne 2
.mk
.na
\fB\fBLINES\fR\fR
.ad
.RS 14n
.rt  
If this variable is set, the value is used to determine the column length for printing select lists. Select lists prints vertically until about two-thirds of \fBLINES\fR lines are filled.
.RE

.sp
.ne 2
.mk
.na
\fB\fBMAIL\fR\fR
.ad
.RS 14n
.rt  
If this variable is set to the name of a mail file \fBand\fR the \fBMAILPATH\fR variable is not set, then the shell informs the user of arrival of mail in the specified file.
.sp
\fBMAIL\fR is not set by the shell. On some systems, \fBMAIL\fR is set by \fBlogin\fR(1).
.RE

.sp
.ne 2
.mk
.na
\fB\fBMAILCHECK\fR\fR
.ad
.RS 14n
.rt  
Specifies how often in seconds the shell checks for changes in the modification time of any of the files specified by the \fBMAILPATH\fR or \fBMAIL\fR variables. The default value is \fB600\fR seconds. When the time has elapsed the shell checks before issuing the next prompt.
.sp
The shell specifies a default value to \fBMAILCHECK\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBMAILPATH\fR\fR
.ad
.RS 14n
.rt  
A colon ( \fB:\fR ) separated list of file names. If this variable is set, then the shell informs the user of any modifications to the specified files that have occurred within the last \fBMAILCHECK\fR seconds. Each file name can be followed by a \fB?\fR and a message that is printed. The message undergoes parameter expansion, command substitution, and arithmetic substitution with the variable \fB$_\fR defined as the name of the file that has changed. The default message is \fByou have mail in $_\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBPATH\fR\fR
.ad
.RS 14n
.rt  
The search path for commands. Except in \fB\&.profile\fR, users cannot change \fBPATH\fR if executing under \fBrksh\fR. See the \fBExecution\fR section of this manual page.
.sp
The shell specifies a default value to \fBPATH\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBPS1\fR\fR
.ad
.RS 14n
.rt  
The value of this variable is expanded for parameter expansion, command substitution, and arithmetic substitution to define the primary prompt string which by default is \fB$\fR. The character \fB!\fR in the primary prompt string is replaced by the command number. Two successive occurrences of \fB!\fR produces a single \fB!\fR when the prompt string is printed. See the \fBCommand Re-entry\fR section of this manual page.
.sp
The shell specifies a default value to \fBPS1\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBPS2\fR\fR
.ad
.RS 14n
.rt  
Secondary prompt string, by default, \fB>\fR.
.sp
The shell specifies a default value to \fBPS2\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBPS3\fR\fR
.ad
.RS 14n
.rt  
Selection prompt string used within a select loop, by default \fB#?\fR.
.sp
The shell specifies a default value to \fBPS3\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBPS4\fR\fR
.ad
.RS 14n
.rt  
The value of this variable is expanded for parameter evaluation, command substitution, and arithmetic substitution and precedes each line of an execution trace. By default, \fBPS4\fR is \fB+\fR. When \fBPS4\fR is unset, the execution trace prompt is also \fB+\fR .
.sp
The shell specifies a default value to \fBPS4\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBSHELL\fR\fR
.ad
.RS 14n
.rt  
The pathname of the shell is kept in the environment. At invocation, if the basename of this variable is \fBrsh\fR, \fBrksh\fR, \fBrksh\fR, or \fBkrsh\fR, the shell becomes restricted.
.sp
\fBSHELL\fR is not set by the shell. On some systems, \fBSHELL\fR is set by \fBlogin\fR(1).
.RE

.sp
.ne 2
.mk
.na
\fB\fBTIMEFORMAT\fR\fR
.ad
.RS 14n
.rt  
The value of this parameter is used as a format string specifying how the timing information for pipelines prefixed with the \fBtime\fR reserved word should be displayed. The \fB%\fR character introduces a format sequence that is expanded to a time value or other information. 
.sp
The format sequences and their meanings are as follows.
.sp
.ne 2
.mk
.na
\fB\fB%%\fR\fR
.ad
.sp .6
.RS 4n
A literal \fB%\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB%[\fIp\fR][l]R\fR\fR
.ad
.sp .6
.RS 4n
The elapsed time in seconds.
.RE

.sp
.ne 2
.mk
.na
\fB\fB%[\fIp\fR][l]U\fR\fR
.ad
.sp .6
.RS 4n
The number of CPU seconds spent in user mode.
.RE

.sp
.ne 2
.mk
.na
\fB\fB%[\fIp\fR][l]S\fR\fR
.ad
.sp .6
.RS 4n
The number of CPU seconds spent in system mode.
.RE

.sp
.ne 2
.mk
.na
\fB\fB%P\fR\fR
.ad
.sp .6
.RS 4n
The CPU percentage, computed as \fB(U + S) / R\fR.
.RE

The braces denote optional portions. The optional \fIp\fR is a digit specifying the \fIprecision\fR, the number of fractional digits after a decimal point. A value of \fB0\fR causes no decimal point or fraction to be output. At most three places after the decimal point can be displayed. Values of \fIp\fR greater than \fB3\fR are treated as \fB3\fR. If \fIp\fR is not specified, the value \fB3\fR is used.
.sp
The optional \fBl\fR specifies a longer format, including hours if greater than zero, minutes, and seconds of the form \fIHHhMMmSS.FFs\fR. The value of \fIp\fR determines whether or not the fraction is included.
.sp
All other characters are output without change and a trailing NEWLINE is added. If unset, the default value, \fB$'\nreal\t%2lR\nuser\t%2lU\nsys%2lS'\fR, is used. If the value is null, no timing information is displayed.
.RE

.sp
.ne 2
.mk
.na
\fB\fBTMOUT\fR\fR
.ad
.RS 14n
.rt  
If set to a value greater than zero, \fBTMOUT\fR is the default time-out value for the \fBread\fR built-in command. The \fBselect\fR compound command terminates after \fBTMOUT\fR seconds when input is from a terminal. Otherwise, the shell terminates if a line is not entered within the prescribed number of seconds while reading from a terminal. The shell can be compiled with a maximum bound for this value which cannot be exceeded.
.sp
The shell specifies a default value to \fBTMOUT\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBVISUAL\fR\fR
.ad
.RS 14n
.rt  
If the value of this variable matches the pattern \fB*[Vv][Ii]*\fR, then the \fBvi\fR option is turned on. See \fBSpecial Commands\fR. If the value matches the pattern \fB*gmacs*\fR , the \fBgmacs\fR option is turned on. If the value matches the pattern \fB*macs*\fR, then the \fBemacs\fR option is turned on. The value of \fBVISUAL\fR overrides the value of \fBEDITOR\fR.
.RE

.SS "Field Splitting"
.sp
.LP
After parameter expansion and command substitution, the results of substitutions are scanned for the field separator characters (those found in \fBIFS\fR) and split into distinct fields where such characters are found. Explicit null fields (\fB""\fR or \fB\&''\fR) are retained. Implicit null fields, those resulting from parameters that have no values or command substitutions with no output, are removed.
.sp
.LP
If the \fBbraceexpand\fR (\fB-B\fR) option is set, each of the fields resulting from \fBIFS\fR are checked to see if they contain one or more of the brace patterns. Valid brace patterns: \fB{*\fR,\fB*}\fR, \fB{\fR\fIl1\fR\fB\&..\fR\fIl2\fR\fB}\fR , \fB{\fR\fIn1\fR\fB\&..\fR\fIn2\fR\fB}\fR, \fB{\fR\fIn1\fR\fB\&..\fR\fIn2\fR\fB%\fR\fIfmt\fR\fB} {\fR\fIn1\fR\fB\&..\fR\fIn2\fR \fB\&..\fR\fIn3\fR\fB}\fR, or \fB{\fR\fIn1\fR\fB\&..\fR\fIn2\fR \fB\&..\fR\fIn3\fR\fB%\fR\fIfmt\fR\fB}\fR , where \fB*\fR represents any character, \fIl1\fR,\fIl2\fR are letters and \fIn1\fR,\fIn2\fR,\fIn3\fR are signed numbers and \fIfmt\fR is a format specified as used by \fBprintf\fR. In each case, fields are created by prepending the characters before the \fB{\fR and appending the characters after the } to each of the strings generated by the characters between the \fB{\fR and \fB}\fR. The resulting fields are checked to see if they have any brace patterns.
.sp
.LP
In the first form, a field is created for each string between \fB{\fR and \fB,,\fR between \fB,\fR and \fB,,\fR and between , and \fB}\fR. The string represented by \fB*\fR can contain embedded matching { and } without quoting. Otherwise, each \fB{\fR and \fB}\fR with \fB*\fR must be quoted.
.sp
.LP
In the second form, \fIl1\fR and \fIl2\fR must both be either upper case or both be lower case characters in the C locale. In this case a field is created for each character from \fIl1\fR through \fIl2\fR.
.sp
.LP
In the remaining forms, a field is created for each number starting at \fIn1\fR. This continues until it reaches \fIn2\fR and increments \fIn1\fR by \fIn3\fR. The cases where \fIn3\fR is not specified behave as if \fIn3\fR were 1 if \fIn1\fR\fB<=\fR\fIn2\fR, and \fB-1\fR otherwise. In forms which specify \fB%\fR\fIfmt\fR, any format flags, widths and precisions can be specified and \fIfmt\fR can end in any of the specifiers \fBcdiouxX\fR. For example, \fB{a,z}{1..5..3%02d}{b..c}x\fR expands to the 8 fields, \fBa01bx, a01cx, a04bx, a04cx, z01bx, z01cx, z04bx,\fR and \fBz4cx\fR.
.SS "File Name Generation"
.sp
.LP
Following splitting, each field is scanned for the characters \fB*\fR, \fB?\fR, \fB(\fR, and \fB[\fR, unless the \fB-f\fR option has been set. If one of these characters appears, then the word is regarded as a pattern. 
.sp
.LP
Each file name component that contains any pattern character is replaced with a lexicographically sorted set of names that matches the pattern from that directory. If no file name is found that matches the pattern, then that component of the file name is left unchanged unless the pattern is prefixed with \fB~(N)\fR in which case it is removed. If \fBFIGNORE\fR is set, then each file name component that matches the pattern defined by the value of \fBFIGNORE\fR is ignored when generating the matching file names. The names \fB\&.\fR and \fB\&..\fR are also ignored. If \fBFIGNORE\fR is not set, the character \fB\&.\fR at the start of each file name component is ignored unless the first character of the pattern corresponding to this component is the character \fB\&.\fR itself. For other uses of pattern matching the \fB/\fR and \fB\&.\fR are not specially treated.
.sp
.ne 2
.mk
.na
\fB\fB*\fR\fR
.ad
.RS 11n
.rt  
Match any string, including the null string. When used for file name expansion, if the \fBglobstar\fR option is on, two adjacent \fB*\fRs by themselves match all files and zero or more directories and subdirectories. If the two adjacent \fB*\fRs are followed by a \fB/\fR, only directories and subdirectories match.
.RE

.sp
.ne 2
.mk
.na
\fB\fB?\fR\fR
.ad
.RS 11n
.rt  
Matches any single character.
.RE

.sp
.ne 2
.mk
.na
\fB[\fB\&...\fR]\fR
.ad
.RS 11n
.rt  
Match any one of the enclosed characters. A pair of characters separated by \fB-\fR matches any character lexically between the pair, inclusive. If the first character following the opening \fB[\fR is a \fB!\fR, any character not enclosed is matched. A \fB-\fR can be included in the character set by putting it as the first or last character. Within \fB[\fR and \fB]\fR, character classes can be specified with the syntax \fB[:\fR\fIclass\fR\fB:]\fR where \fIclass\fR is one of the following classes defined in the \fBANSI-C\fR standard:
.sp
.in +2
.nf
\fIalnum alpha blank cntrl digit graph\fR
\fIlower print punct space upper\fR
\fIword xdigit\fR
.fi
.in -2
.sp

\fIword\fR is equivalent to \fIalnum\fR plus the character \fB_\fR. Within \fB[\fR and \fB]\fR, an equivalence class can be specified with the syntax \fB[=\fR\fIc\fR\fB=]\fR which matches all characters with the same primary collation weight (as defined by the current locale) as the character \fIc\fR. Within \fB[\fR and \fB]\fR, [\fI\&.symbol.\fR] matches the collating symbol \fIsymbol\fR.
.RE

.sp
.LP
A \fIpattern-list\fR is a list of one or more patterns separated from each other with an \fB&\fR or \fB|\fR. An \fB&\fR signifies that all patterns must be matched whereas \fB|\fR requires that only one pattern be matched. Composite patterns can be formed with one or more of the following sub-patterns:
.sp
.ne 2
.mk
.na
\fB\fB?(\fR\fIpattern-list\fR\fB)\fR\fR
.ad
.RS 23n
.rt  
Optionally matches any one of the specified patterns.
.RE

.sp
.ne 2
.mk
.na
\fB\fB*(\fR\fIpattern-list\fR\fB)\fR\fR
.ad
.RS 23n
.rt  
Matches zero or more occurrences of the specified patterns.
.RE

.sp
.ne 2
.mk
.na
\fB\fB+(\fR\fIpattern-list\fR\fB)\fR\fR
.ad
.RS 23n
.rt  
Matches one or more occurrences of the specified patterns.
.RE

.sp
.ne 2
.mk
.na
\fB\fB{\fR\fIn\fR\fB}(\fR\fIpattern-list\fR\fB)\fR\fR
.ad
.RS 23n
.rt  
Matches \fIn\fR occurrences of the specified patterns.
.RE

.sp
.ne 2
.mk
.na
\fB\fB{\fR\fIm\fR\fB,\fR\fIn\fR\fB}(\fR\fIpattern-list\fR\fB)\fR\fR
.ad
.RS 23n
.rt  
Matches from \fIm\fR to \fIn\fR occurrences of the specified patterns. If \fIm\fR is omitted, \fB0\fR is used. If \fIn\fR is omitted at least \fIm\fR occurrences are matched.
.RE

.sp
.ne 2
.mk
.na
\fB\fB@(\fR\fIpattern-list\fR\fB)\fR\fR
.ad
.RS 23n
.rt  
Matches exactly one of the specified patterns.
.RE

.sp
.ne 2
.mk
.na
\fB\fB!(\fR\fIpattern-list\fR\fB)\fR\fR
.ad
.RS 23n
.rt  
Matches anything except one of the specified patterns.
.RE

.sp
.LP
By default, each pattern, or sub-pattern matches the longest string possible consistent with generating the longest overall match. If more than one match is possible, the one starting closest to the beginning of the string is chosen. However, for each of the compound patterns a \fB-\fR can be inserted in front of the \fB(\fR to cause the shortest match to the specified \fIpattern-list\fR to be used.
.sp
.LP
When \fIpattern-list\fR is contained within parentheses, the backslash character \fB\e\fR is treated specially even when inside a character class. All \fBANSI-C\fR character escapes are recognized and match the specified character. In addition the following escape sequences are recognized:
.sp
.ne 2
.mk
.na
\fB\fB\ed\fR\fR
.ad
.RS 7n
.rt  
Matches any character in the digit class.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\eD\fR\fR
.ad
.RS 7n
.rt  
Matches any character not in the digit class.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\es\fR\fR
.ad
.RS 7n
.rt  
Matches any character in the space class.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\eS\fR\fR
.ad
.RS 7n
.rt  
Matches any character not in the space class.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\ew\fR\fR
.ad
.RS 7n
.rt  
Matches any character in the word class.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\eW\fR\fR
.ad
.RS 7n
.rt  
Matches any character not in the word class.
.RE

.sp
.LP
A pattern of the form \fB%(\fR\fIpattern-pairs\fR\fB)\fR is a sub-pattern that can be used to match nested character expressions. Each \fIpattern-pair\fR is a two character sequence which cannot contain \fB&\fR or \fB|\fR. The first \fIpattern-pair\fR specifies the starting and ending characters for the match. Each subsequent \fIpattern-pair\fR represents the beginning and ending characters of a nested group that is skipped over when counting starting and ending character matches. The behavior is unspecified when the first character of a \fIpattern-pair\fR is alphanumeric except for the following:
.sp
.ne 2
.mk
.na
\fB\fBD\fR\fR
.ad
.RS 5n
.rt  
Causes the ending character to terminate the search for this pattern without finding a match.
.RE

.sp
.ne 2
.mk
.na
\fB\fBE\fR\fR
.ad
.RS 5n
.rt  
Causes the ending character to be interpreted as an escape character.
.RE

.sp
.ne 2
.mk
.na
\fB\fBL\fR\fR
.ad
.RS 5n
.rt  
Causes the ending character to be interpreted as a quote character causing all characters to be ignored when looking for a match.
.RE

.sp
.ne 2
.mk
.na
\fB\fBQ\fR\fR
.ad
.RS 5n
.rt  
Causes the ending character to be interpreted as a quote character causing all characters other than any escape character to be ignored when looking for a match.
.RE

.sp
.LP
\fB%({}Q"E\e)\fR, matches characters starting at \fB{\fR until the matching \fB}\fR is found not counting any \fB{\fR or \fB}\fR that is inside a double quoted string or preceded by the escape character \fB\e\fR\&. Without the \fB{}\fR this pattern matches any C language string.
.sp
.LP
Each sub-pattern in a composite pattern is numbered, starting at \fB1\fR, by the location of the \fB(\fR within the pattern. The sequence \fB\e\fR\fIn\fR, where \fIn\fR is a single digit and \fB\e\fR\fIn\fR comes after the \fIn\fRth. sub-pattern, matches the same string as the sub-pattern itself.
.sp
.LP
A pattern can contain sub-patterns of the form \fB~(\fR\fIoptions\fR\fB:\fR\fIpattern-list\fR\fB)\fR, where either \fIoptions\fR or \fB:\fR\fIpattern-list\fR can be omitted. Unlike the other compound patterns, these sub-patterns are not counted in the numbered sub-patterns. If \fIoptions\fR is present, it can consist of one or more of the following:
.sp
.ne 2
.mk
.na
\fB\fB+\fR\fR
.ad
.RS 5n
.rt  
Enable the following options. This is the default.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-\fR\fR
.ad
.RS 5n
.rt  
Disable the following options.
.RE

.sp
.ne 2
.mk
.na
\fB\fBE\fR\fR
.ad
.RS 5n
.rt  
The remainder of the pattern uses extended regular expression syntax like the \fBegrep\fR(1) command.
.RE

.sp
.ne 2
.mk
.na
\fB\fBF\fR\fR
.ad
.RS 5n
.rt  
The remainder of the pattern uses \fBfgrep\fR(1) expression syntax.
.RE

.sp
.ne 2
.mk
.na
\fB\fBg\fR\fR
.ad
.RS 5n
.rt  
File the longest match (greedy). 
.sp
This is the default.
.RE

.sp
.ne 2
.mk
.na
\fB\fBG\fR\fR
.ad
.RS 5n
.rt  
The remainder of the pattern uses basic regular expression syntax like the \fBgrep\fR(1) command.
.RE

.sp
.ne 2
.mk
.na
\fB\fBi\fR\fR
.ad
.RS 5n
.rt  
Treat the match as case insensitive.
.RE

.sp
.ne 2
.mk
.na
\fB\fBK\fR\fR
.ad
.RS 5n
.rt  
The remainder of the pattern uses shell pattern syntax. 
.sp
This is the default.
.RE

.sp
.ne 2
.mk
.na
\fB\fBl\fR\fR
.ad
.RS 5n
.rt  
Left anchor the pattern. 
.sp
This is the default for \fBK\fR style patterns.
.RE

.sp
.ne 2
.mk
.na
\fB\fBN\fR\fR
.ad
.RS 5n
.rt  
This is ignored. However, when it is the first letter and is used with file name generation, and no matches occur, the file pattern expands to the empty string.
.RE

.sp
.ne 2
.mk
.na
\fB\fBr\fR\fR
.ad
.RS 5n
.rt  
Right anchor the pattern. 
.sp
This is the default for \fBK\fR style patterns.
.RE

.sp
.LP
If both \fIoptions\fR and \fB:\fR\fIpattern-list\fR are specified, then the options apply only to \fIpattern-list\fR. Otherwise, these options remain in effect until they are disabled by a subsequent \fB~(...)\fR or at the end of the sub-pattern containing \fB~(...)\fR.
.SS "Quoting"
.sp
.LP
Each of the metacharacters listed in the \fBDefinitions\fR has a special meaning to the shell.
.sp
.ne 2
.mk
.na
\fB\fBg\fR\fR
.ad
.RS 5n
.rt  
File the longest match (greedy). This is the default.
.RE

.sp
.ne 2
.mk
.na
\fB\fBi\fR\fR
.ad
.RS 5n
.rt  
Treat the match as case insensitive. 
.RE

.sp
.LP
If both \fIoptions\fR and \fB:\fR\fIpattern-list\fR are specified, then the options apply only to \fIpattern-list\fR. Otherwise, the options remain in effect until they are disabled by a subsequent \fB~(...)\fR or at the end of the sub-pattern containing \fB~(...)\fR.
.sp
.LP
Each of the metacharacters listed in the \fBDefinitions\fR section of this manual page has a special meaning to the shell and causes termination of a word unless quoted. A character can be quoted, that is, made to stand for itself, by preceding it with a backslash (\fB\e\fR). The pair \fB\e\fRNEWLINE is removed. All characters enclosed between a pair of single quote marks (\fB\&''\fR) that is not preceded by a \fB$\fR are quoted. A single quote cannot appear within the single quotes. A single quoted string preceded by an unquoted \fB$\fR is processed as an \fBANSI-C\fR string except for the following:
.sp
.ne 2
.mk
.na
\fB\fB\e0\fR\fR
.ad
.RS 19n
.rt  
Causes the remainder of the string to be ignored.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\ec\fR\fIx\fR\fR
.ad
.RS 19n
.rt  
Expands to the character CTRL-x.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\eC\fR[\fB\&.\fR\fIname\fR\fB\&.\fR]\fR
.ad
.RS 19n
.rt  
Expands to the collating element \fIname\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\ee\fR\fR
.ad
.RS 19n
.rt  
Equivalent to the escape character (\fBASCII\fR 033),
.RE

.sp
.ne 2
.mk
.na
\fB\fB\eE\fR\fR
.ad
.RS 19n
.rt  
Equivalent to the escape character (\fBASCII\fR 033),
.RE

.sp
.LP
Inside double quote marks (\fB""\fR), parameter and command substitution occur and \fB\e\fR quotes the characters \fB\e\fR, \fB`\fR, \fB"\fR, and \fB$\fR. A \fB$\fR in front of a double quoted string is ignored in the \fBC\fR or \fBPOSIX\fR locale, and might cause the string to be replaced by a locale specific string otherwise. The meaning of \fB$*\fR and \fB$@\fR is identical when not quoted or when used as a variable assignment value or as a file name. However, when used as a command argument, \fB"$*"\fR is equivalent to \fB"$1\fId\fR$2\fId\fR..."\fR, where \fId\fR is the first character of the IFS variable, whereas \fB"$@"\fR is equivalent to \fB"$1" "$2" ....\fR Inside grave quote marks (\fB``\fR), \fB\\fR quotes the characters \fB\e\fR, \fB`\fR, and \fB$\fR. If the grave quotes occur within double quotes, then \fB\e\fR also quotes the character \fB"\fR.
.sp
.LP
The special meaning of reserved words or aliases can be removed by quoting any character of the reserved word. The recognition of function names or built-in command names cannot be altered by quoting them.
.SS "Arithmetic Evaluation"
.sp
.LP
The shell performs arithmetic evaluation for arithmetic substitution, to evaluate an arithmetic command, to evaluate an indexed array subscript, and to evaluate arguments to the built-in commands \fBshift\fR and \fBlet\fR. Arithmetic evaluation is also performed on argument operands of the built-in command printf that correspond to numeric format specifiers in the format operand. See \fBprintf\fR(1). Evaluations are performed using double precision floating point arithmetic or long double precision floating point for systems that provide this data type. Floating point constants follow the \fBANSI-C\fR programming language floating point conventions. Integer constants follow the \fBANSI-C\fR programming language integer constant conventions although only single byte character constants are recognized and character casts are not recognized. Constants can be of the form \fB[\fR\fIbase#\fR\fB]\fR\fIn\fR where \fIbase\fR is a decimal number between two and sixty-four representing the arithmetic base and \fIn\fR is a number in that base. The digits greater than \fB9\fR are represented by the lower case letters, the upper case letters, \fB@\fR, and \fB_\fR respectively. For bases less than or equal to \fB36\fR, upper and lower case characters can be used interchangeably.
.sp
.LP
An arithmetic expression uses the same syntax, precedence, and associativity of expression as the C language. All the C language operators that apply to floating point quantities can be used. In addition, the operator \fB**\fR can be used for exponentiation. It has higher precedence than multiplication and is left associative. When the value of an arithmetic variable or subexpression can be represented as a long integer, all C language integer arithmetic operations can be performed. Variables can be referenced by name within an arithmetic expression without using the parameter expansion syntax. When a variable is referenced, its value is evaluated as an arithmetic expression. 
.sp
.LP
Any of the following math library functions that are in the C math library can be used within an arithmetic expression:
.sp
.in +2
.nf
abs acos acosh asin asinh atan atan2 atanh cbrt 
copysign cos cosh erf erfc exp exp2 expm1 fabs
fdim finite floor fma fmax fmod hypot ilogb 
int isinf isnan lgamma log log2 logb 
nearbyint nextafter nexttoward pow remainder
rint round sin sinh sqrt tan tanh tgamma trunc
.fi
.in -2
.sp

.sp
.LP
An internal representation of a \fIvariable\fR as a double precision floating point can be specified with the \fB-E [\fR\fIn\fR\fB]\fR or \fB-F [\fR\fIn\fR\fB]\fR option of the \fBtypeset\fR special built-in command. The \fB-E\fR option causes the expansion of the value to be represented using scientific notation when it is expanded. The optional option argument \fIn\fR defines the number of significant figures. The \fB-F\fR option causes the expansion to be represented as a floating decimal number when it is expanded. The optional option argument \fIn\fR defines the number of places after the decimal point in this case.
.sp
.LP
An internal integer representation of a \fIvariable\fR can be specified with the \fB-i\fR \fB[\fR\fIn\fR\fB]\fR option of the \fBtypeset\fR special built-in command. The optional option argument \fIn\fR specifies an arithmetic base to be used when expanding the variable. If you do not specify an arithmetic base, base 10 is used.
.sp
.LP
Arithmetic evaluation is performed on the value of each assignment to a variable with the \fB-E\fR, \fB-F\fR, or \fB-i\fR option. Assigning a floating point number to a variable whose type is an integer causes the fractional part to be truncated. 
.SS "Prompting"
.sp
.LP
When used interactively, the shell prompts with the value of \fBPS1\fR after expanding it for parameter expansion, command substitution, and arithmetic substitution, before reading a command. In addition, each single \fB!\fR in the prompt is replaced by the command number. A \fB!!\fR is required to place \fB!\fR in the prompt. If at any time a NEWLINE is typed and further input is needed to complete a command, then the secondary prompt, that is, the value of \fBPS2\fR, is issued.
.SS "Conditional Expressions"
.sp
.LP
A \fBconditional expression\fR is used with the \fB[[\fR compound command to test attributes of files and to compare strings. Field splitting and file name generation are not performed on the words between \fB[[\fR and \fB]]\fR.
.sp
.LP
Each expression can be constructed from one or more of the following unary or binary expressions:
.sp
.ne 2
.mk
.na
\fB\fB-a\fR \fIfile\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile\fR exists.
.sp
This option is the same as \fB-e\fR. This option is obsolete.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-b\fR \fIfile\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile\fR exists and is a block special file.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-c\fR \fIfile\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile\fR exists and is a character special file.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-d\fR \fIfile\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile\fR exists and is a directory.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-e\fR \fIfile\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile\fR exists.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-f\fR \fIfile\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile\fR exists and is an ordinary file.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-g\fR \fIfile\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile\fR exists and it has its \fBsetgid\fR bit set.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-G\fR \fIfile\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile\fR exists and its group matches the effective group id of this process.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-h\fR \fIfile\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile\fR exists and is a symbolic link.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-k\fR \fIfile\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile\fR exists and it has its sticky bit set.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-L\fR \fIfile\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile\fR exists and is a symbolic link.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-n\fR \fIstring\fR\fR
.ad
.RS 21n
.rt  
True, if length of \fIstring\fR is \fBnon-zero\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-N\fR \fIfile\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile\fR exists and the modification time is greater than the last access time.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-o\fR \fIoption\fR\fR
.ad
.RS 21n
.rt  
True, if option named \fIoption\fR is on.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-o\fR \fI?option\fR\fR
.ad
.RS 21n
.rt  
True, if option named \fIoption\fR is a valid option name.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-O\fR \fIfile\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile\fR exists and is owned by the effective user id of this process.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-p\fR \fIfile\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile\fR exists and is a \fBFIFO\fR special file or a pipe.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-r\fR \fIfile\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile\fR exists and is readable by current process.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-s\fR \fIfile\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile\fR exists and has size greater than zero.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-S\fR \fIfile\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile\fR exists and is a socket.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-t\fR \fIfildes\fR\fR
.ad
.RS 21n
.rt  
True, if file descriptor number \fIfildes\fR is open and associated with a terminal device.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-u\fR \fIfile\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile\fR exists and it has its \fBsetuid\fR bit set.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-w\fR \fIfile\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile\fR exists and is writable by current process.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-x\fR \fIfile\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile\fR exists and is executable by current process. If \fIfile\fR exists and is a directory, then true if the current process has permission to search in the directory.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-z\fR \fIstring\fR\fR
.ad
.RS 21n
.rt  
True, if length of \fIstring\fR is zero.
.RE

.sp
.ne 2
.mk
.na
\fB\fIfile1\fR \fB-ef\fR \fIfile2\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile1\fR and \fIfile2\fR exist and refer to the same file.
.RE

.sp
.ne 2
.mk
.na
\fB\fIfile1\fR \fB-nt\fR \fIfile2\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile1\fR exists and \fIfile2\fR does not, or \fIfile1\fR is newer than \fIfile2\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fIfile1\fR \fB-ot\fR \fIfile2\fR\fR
.ad
.RS 21n
.rt  
True, if \fIfile2\fR exists and \fIfile1\fR does not, or \fIfile1\fR is older than \fIfile2\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fIstring\fR\fR
.ad
.RS 21n
.rt  
True, if \fIstring\fR is not null.
.RE

.sp
.ne 2
.mk
.na
\fB\fIstring\fR \fB==\fR \fIpattern\fR\fR
.ad
.RS 21n
.rt  
True, if \fIstring\fR matches \fIpattern\fR. Any part of \fIpattern\fR can be quoted to cause it to be matched as a string. With a successful match to \fIpattern\fR, the \fB\&.sh.match\fR array variable contains the match and sub-pattern matches.
.RE

.sp
.ne 2
.mk
.na
\fB\fIstring\fR \fB=\fR \fIpattern\fR\fR
.ad
.RS 21n
.rt  
Same as \fB==\fR, but is obsolete.
.RE

.sp
.ne 2
.mk
.na
\fB\fIstring\fR \fB!=\fR \fIpattern\fR\fR
.ad
.RS 21n
.rt  
True, if \fIstring\fR does not match \fIpattern\fR. When the \fIstring\fR matches the \fIpattern\fR the \fB\&.sh.match\fR array variable contains the match and sub-pattern matches.
.RE

.sp
.ne 2
.mk
.na
\fB\fIstring\fR \fB=~\fR \fIere\fR\fR
.ad
.RS 21n
.rt  
True if \fIstring\fR matches the pattern \fB~(E)\fR\fIere\fR where \fIere\fR is an extended regular expression.
.RE

.sp
.ne 2
.mk
.na
\fB\fIstring1\fR \fB<\fR \fIstring2\fR\fR
.ad
.RS 21n
.rt  
True, if \fIstring1\fR comes before \fIstring2\fR based on \fBASCII\fR value of their characters.
.RE

.sp
.ne 2
.mk
.na
\fB\fIstring1\fR \fB>\fR \fIstring2\fR\fR
.ad
.RS 21n
.rt  
True, if \fIstring1\fR comes after \fIstring2\fR based on \fBASCII\fR value of their characters.
.RE

.sp
.LP
In each of the following expressions, if \fIfile\fR is of the form \fB/dev/fd/\fR\fIn\fR, where \fIn\fR is an integer, the test is applied to the open file whose descriptor number is \fIn\fR. The following obsolete arithmetic comparisons are supported: 
.sp
.ne 2
.mk
.na
\fB\fIexp1\fR \fB-eq\fR \fIexp2\fR\fR
.ad
.RS 17n
.rt  
True, if \fIexp1\fR is equal to \fIexp2\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fIexp1\fR \fB-ge\fR \fIexp2\fR\fR
.ad
.RS 17n
.rt  
True, if \fIexp1\fR is greater than or equal to \fIexp2\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fIexp1\fR \fB-gt\fR \fIexp2\fR\fR
.ad
.RS 17n
.rt  
True, if \fIexp1\fR is greater than \fIexp2\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fIexp1\fR \fB-le\fR \fIexp2\fR\fR
.ad
.RS 17n
.rt  
True, if \fIexp1\fR is less than or equal to \fIexp2\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fIexp1\fR \fB-lt\fR \fIexp2\fR\fR
.ad
.RS 17n
.rt  
True, if \fIexp1\fR is less than \fIexp2\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fIexp1\fR \fB-ne\fR \fIexp2\fR\fR
.ad
.RS 17n
.rt  
True, if \fIexp1\fR is not equal to \fIexp2\fR.
.RE

.sp
.LP
A compound expression can be constructed from these primitives by using any of the following, listed in decreasing order of precedence:
.sp
.ne 2
.mk
.na
\fB\fB(\fR\fIexpression\fR\fB)\fR\fR
.ad
.RS 30n
.rt  
True, if \fIexpression\fR is true. Used to group expressions.
.RE

.sp
.ne 2
.mk
.na
\fB\fB!\fR \fIexpression\fR\fR
.ad
.RS 30n
.rt  
True, if \fIexpression\fR is false.
.RE

.sp
.ne 2
.mk
.na
\fB\fIexpression1\fR \fB&&\fR \fIexpression2\fR\fR
.ad
.RS 30n
.rt  
True, if \fIexpression1\fR and \fIexpression2\fR are both true.
.RE

.sp
.ne 2
.mk
.na
\fB\fIexpression1\fR \fB||\fR \fIexpression2\fR\fR
.ad
.RS 30n
.rt  
True, if either \fIexpression1\fR or \fIexpression2\fR is true.
.RE

.SS "Input and Output"
.sp
.LP
Before a command is executed, its input and output can be redirected using a special notation interpreted by the shell. The following can appear anywhere in a simple command or can precede or follow a command and are \fBnot\fR passed on to the invoked command. Command substitution, parameter expansion, and arithmetic substitution occur before \fIword\fR or \fIdigit\fR is used except as noted in this section. File name generation occurs only if the shell is interactive and the pattern matches a single file. Field splitting is not performed.
.sp
.LP
In each of the following redirections, if \fIfile\fR is of the form \fB/dev/sctp/\fR\fIhost\fR\fB/\fR\fIport\fR, \fB/dev/tcp/\fR\fIhost\fR\fB/\fR\fIport\fR, or \fB/dev/udp/\fR\fIhost\fR\fB/\fR\fIport\fR, where \fIhost\fR is a hostname or host address, and \fIport\fR is a service specified by name or an integer port number, then the redirection attempts to make a \fBtcp\fR, \fBsctp\fR or \fBudp\fR connection to the corresponding socket.
.sp
.LP
No intervening space is allowed between the characters of redirection operators.
.sp
.ne 2
.mk
.na
\fB\fB<\fR\fIword\fR\fR
.ad
.RS 14n
.rt  
Use file \fIword\fR as standard input (file descriptor 0). 
.RE

.sp
.ne 2
.mk
.na
\fB\fB>\fR\fIword\fR\fR
.ad
.RS 14n
.rt  
Use file \fIword\fR as standard output (file descriptor 1). If the file does not exist then it is created. If the file exists, and the \fBnoclobber\fR option is on, this causes an error. Otherwise, it is truncated to zero length.
.RE

.sp
.ne 2
.mk
.na
\fB\fB>|\fR\fIword\fR\fR
.ad
.RS 14n
.rt  
Same as \fB>\fR, except that it overrides the \fBnoclobber\fR option.
.RE

.sp
.ne 2
.mk
.na
\fB\fB>>\fR\fIword\fR\fR
.ad
.RS 14n
.rt  
Use file \fIword\fR as standard output. If the file exists, then output is appended to it (by first seeking to the end-of-file). Otherwise, the file is created. 
.RE

.sp
.ne 2
.mk
.na
\fB\fB<>\fR\fIword\fR\fR
.ad
.RS 14n
.rt  
Open file \fIword\fR for reading and writing as standard input.
.RE

.sp
.ne 2
.mk
.na
\fB\fB<<\fR\fB[-]\fR\fIword\fR\fR
.ad
.RS 14n
.rt  
The shell input is read up to a line that is the same as \fIword\fR after any quoting has been removed, or to an end-of-file. No parameter substitution, command substitution, arithmetic substitution or file name generation is performed on \fIword\fR. The resulting document, called a \fBhere-document\fR, becomes the standard input. If any character of \fIword\fR is quoted, then no interpretation is placed upon the characters of the document. Otherwise, parameter expansion, command substitution, and arithmetic substitution occur, \fB\e\fRNEWLINE is ignored, and \fB\e\fR must be used to quote the characters \fB\e\fR, \fB$\fR, \fB`\fR\&. If \fB-\fR is appended to \fB<<\fR, then all leading tabs are stripped from \fIword\fR and from the document. If \fB#\fR is appended to \fB<<\fR, then leading SPACEs and TABs are stripped off the first line of the document and up to an equivalent indentation is stripped from the remaining lines and from \fIword\fR. A tab stop is assumed to occur at every 8 columns for the purposes of determining the indentation.
.RE

.sp
.ne 2
.mk
.na
\fB\fB<<<\fR\fIword\fR\fR
.ad
.RS 14n
.rt  
A short form of here document in which \fIword\fR becomes the contents of the here-document after any parameter expansion, command substitution, and arithmetic substitution occur.
.RE

.sp
.ne 2
.mk
.na
\fB\fB<&\fR\fIdigit\fR\fR
.ad
.RS 14n
.rt  
The standard input is duplicated from file descriptor \fIdigit\fR, and similarly for the standard output using \fB>&\fR\fIdigit\fR. See \fBdup\fR(2).
.RE

.sp
.ne 2
.mk
.na
\fB\fB<&\fR\fIdigit\fR\fB-\fR\fR
.ad
.RS 14n
.rt  
The file descriptor specified by \fIdigit\fR is moved to standard input. Similarly for the standard output using \fB>&\fR\fIdigit\fR\fB-\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB<&-\fR\fR
.ad
.RS 14n
.rt  
The standard input is closed. Similarly for the standard output using \fB>&-\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB<&p\fR\fR
.ad
.RS 14n
.rt  
The input from the co-process is moved to standard input. 
.RE

.sp
.ne 2
.mk
.na
\fB\fB>&p\fR\fR
.ad
.RS 14n
.rt  
The output to the co-process is moved to standard output.
.RE

.sp
.ne 2
.mk
.na
\fB\fB<#((\fR\fIexpr\fR\fB))\fR\fR
.ad
.RS 14n
.rt  
Evaluate arithmetic expression \fIexpr\fR and position file descriptor 0 to the resulting value bytes from the start of the file. The variables \fBCUR\fR and \fBEOF\fR evaluate to the current offset and end-of-file offset respectively when evaluating \fIexpr\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB>#((\fR\fIexpr\fR\fB))\fR\fR
.ad
.RS 14n
.rt  
The same as \fB<#\fR except applies to file descriptor 1.
.RE

.sp
.ne 2
.mk
.na
\fB\fB<#\fR\fIpattern\fR\fR
.ad
.RS 14n
.rt  
Seek forward to the beginning of the next line containing pattern.
.RE

.sp
.ne 2
.mk
.na
\fB\fB<##\fR\fIpattern\fR\fR
.ad
.RS 14n
.rt  
The same as \fB<#\fR, except that the portion of the file that is skipped is copied to standard output.
.RE

.sp
.LP
If one of the redirection operators is preceded by a digit, with no intervening space, then the file descriptor number referred to is that specified by the digit (instead of the default 0 or 1). If one of the redirection operators other than \fB>&-\fR and the \fB>#\fR and \fB<#\fR forms, is preceded by \fB{\fR\fIvarname\fR\fB}\fR with no intervening space, then a file descriptor number \fB> 10\fR is selected by the shell and stored in the variable \fIvarname\fR. If \fB>&-\fR or the any of the \fB>#\fR and \fB<#\fR forms is preceded by \fB{\fR\fIvarname\fR\fB}\fR the value of \fIvarname\fR defines the file descriptor to close or position. For example:
.sp
.in +2
.nf
\&... 2>&1
.fi
.in -2
.sp

.sp
.LP
means file descriptor 2 is to be opened for writing as a duplicate of file descriptor 1 and
.sp
.in +2
.nf
exec [\fIn\fR]<\fIfile\fR
.fi
.in -2
.sp

.sp
.LP
means open \fIfile\fR for reading and store the file descriptor number in variable \fIn\fR. The order in which redirections are specified is significant. The shell evaluates each redirection in terms of the (\fIfile_descriptor\fR, \fIfile\fR) association at the time of evaluation. For example:
.sp
.in +2
.nf
\&... 1>\fIfname\fR 2>&1
.fi
.in -2
.sp

.sp
.LP
first associates file descriptor 1 with file \fIfname\fR. It then associates file descriptor 2 with the file associated with file descriptor 1, that is, \fIfname\fR. If the order of redirections were reversed, file descriptor 2 would be associated with the terminal (assuming file descriptor 1 had been) and then file descriptor 1 would be associated with file \fIfname\fR. If a command is followed by \fB&\fR and job control is not active, the default standard input for the command is the empty file \fB/dev/null\fR. Otherwise, the environment for the execution of a command contains the file descriptors of the invoking shell as modified by input and output specifications.
.SS "Environment"
.sp
.LP
The \fIenvironment\fR is a list of name-value pairs that is passed to an executed program in the same way as a normal argument list. See \fBenviron\fR(5).
.sp
.LP
The names must be \fIidentifiers\fR and the values are character strings. The shell interacts with the environment in several ways. On invocation, the shell scans the environment and creates a variable for each name found, giving it the corresponding value and attributes and marking it \fBexport\fR. Executed commands inherit the environment. If the user modifies the values of these variables or creates new ones, using the \fBexport\fR or \fBtypeset\fR \fB-x\fR commands, they become part of the environment. The environment seen by any executed command is thus composed of any name-value pairs originally inherited by the shell, whose values can be modified by the current shell, plus any additions which must be noted in \fBexport\fR or \fBtypeset\fR \fB-x\fR commands. The environment for any simple-command or function can be augmented by prefixing it with one or more variable assignments. A variable assignment argument is a word of the form \fIidentifier\fR\fB=\fR\fIvalue\fR. Thus:
.sp
.in +2
.nf
TERM=450 cmd args
.fi
.in -2
.sp

.sp
.LP
and 
.sp
.in +2
.nf
(export TERM; TERM=450; cmd args)
.fi
.in -2
.sp

.sp
.LP
are equivalent (as far as the execution of \fIcmd\fR is concerned except for special built-in commands listed in the \fBBuilt-Ins\fR section, those that are preceded with a dagger. If the obsolete \fB-k\fR option is set, all variable assignment arguments are placed in the environment, even if they occur after the command name. 
.sp
.LP
The following example first prints \fBa=b c\fR and then \fBc\fR:
.sp
.in +2
.nf
echo a=b c
set -k
echo a=b c
.fi
.in -2
.sp

.sp
.LP
This feature is intended for use with scripts written for early versions of the shell and its use in new scripts is strongly discouraged.
.SS "Functions"
.sp
.LP
For historical reasons, there are two ways to define functions, the \fBname()\fR syntax and the \fBfunction\fR \fBname\fR syntax. These are described in the \fBCommands\fR section of this manual page. 
.sp
.LP
Shell functions are read in and stored internally. Alias names are resolved when the function is read. Functions are executed like commands with the arguments passed as positional parameters. See the \fBExecution\fR section of this manual page for details.
.sp
.LP
Functions defined by the \fBfunction\fR \fBname\fR syntax and called by name execute in the same process as the caller and share all files and present working directory with the caller. Traps caught by the caller are reset to their default action inside the function. A trap condition that is not caught or ignored by the function causes the function to terminate and the condition to be passed on to the caller. A trap on \fBEXIT\fR set inside a function is executed in the environment of the caller after the function completes. Ordinarily, variables are shared between the calling program and the function. However, the \fBtypeset\fR special built-in command used within a function defines local variables whose scope includes the current function. They can be passed to functions that they call in the variable assignment list that precedes the call or as arguments passed as name references. Errors within functions return control to the caller.
.sp
.LP
Functions defined with the \fBname()\fR syntax and functions defined with the \fBfunction\fR \fBname\fR syntax that are invoked with the \fB\&.\fR special built-in are executed in the caller's environment and share all variables and traps with the caller. Errors within these function executions cause the script that contains them to abort.
.sp
.LP
The special built-in command \fBreturn\fR is used to return from function calls.
.sp
.LP
Function names can be listed with the \fB-f\fR or \fB+f\fR option of the \fBtypeset\fR special built-in command. The text of functions, when available, is also listed with \fB-f\fR. Functions can be undefined with the \fB-f\fR option of the \fBunset\fR special built-in command.
.sp
.LP
Ordinarily, functions are unset when the shell executes a shell script. Functions that need to be defined across separate invocations of the shell should be placed in a directory and the \fBFPATH\fR variable should contain the name of this directory. They can also be specified in the \fBENV\fR file.
.SS "Discipline Functions"
.sp
.LP
Each variable can have zero or more discipline functions associated with it. The shell initially understands the discipline names \fBget\fR, \fBset\fR, \fBappend\fR, and \fBunset\fR but on most systems others can be added at run time via the C programming interface extension provided by the \fBbuiltin\fR built-in utility. If the \fBget\fR discipline is defined for a variable, it is invoked whenever the specified variable is referenced. If the variable \fB\&.sh.value\fR is assigned a value inside the discipline function, the referenced variable is evaluated to this value instead. If the \fBset\fR discipline is defined for a variable, it is invoked whenever the specified variable is assigned a value. If the \fBappend\fR discipline is defined for a variable, it is invoked whenever a value is appended to the specified variable. The variable \fB\&.sh.value\fR is specified the value of the variable before invoking the discipline, and the variable is assigned the value of \fB\&.sh.value\fR after the discipline completes. If .\fBsh.value\fR is \fBunset\fR inside the discipline, then that value is unchanged. If the \fBunset\fR discipline is defined for a variable, it is invoked whenever the specified variable is unset. The variable is not unset unless it is unset explicitly from within this discipline function.
.sp
.LP
The variable \fB\&.sh.name\fR contains the name of the variable for which the discipline function is called, \fB\&.sh.subscript\fR is the subscript of the variable, and \fB\&.sh.value\fR contains the value being assigned inside the \fBset\fR discipline function. For the \fBset\fR discipline, changing \fB\&.sh.value\fR changes the value that gets assigned. 
.SS "Jobs"
.sp
.LP
If the monitor option of the \fBset\fR command is turned on, an interactive shell associates a job with each pipeline. It keeps a table of current jobs, printed by the \fBjobs\fR command, and assigns them small integer numbers. When a job is started asynchronously with \fB&\fR, the shell prints a line which looks like:
.sp
.in +2
.nf
[1] 1234
.fi
.in -2
.sp

.sp
.LP
indicating that the job which was started asynchronously was job number 1 and had one (top-level) process, whose process id was \fB1234\fR.
.sp
.LP
If you are running a job and wish to stop it, CTRL-z sends a \fBSTOP\fR signal to the current job. The shell normally displays a message that the job has been stopped, and displays another prompt. You can then manipulate the state of this job, putting it in the background with the \fBbg\fR command, or run some other commands and then eventually bring the job back into the foreground with the foreground command \fBfg\fR. A CTRL-z takes effect immediately and is like an interrupt in that pending output and unread input are discarded when it is typed.
.sp
.LP
A job being run in the background stops if it tries to read from the terminal. Background jobs are normally allowed to produce output, but this can be disabled by giving the command \fBsttytostop\fR. If you set this \fBtty\fR option, then background jobs stop when they try to produce output like they do when they try to read input. 
.sp
.LP
There are several ways to refer to jobs in the shell. A job can be referred to by the process id of any process of the job or by one of the following:
.sp
.ne 2
.mk
.na
\fB\fB%\fR\fInumber\fR\fR
.ad
.RS 12n
.rt  
The job with the specified number.
.RE

.sp
.ne 2
.mk
.na
\fB\fB%\fR\fIstring\fR\fR
.ad
.RS 12n
.rt  
Any job whose command line begins with \fIstring\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB%?\fR\fIstring\fR\fR
.ad
.RS 12n
.rt  
Any job whose command line contains \fIstring\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB%%\fR\fR
.ad
.RS 12n
.rt  
Current job.
.RE

.sp
.ne 2
.mk
.na
\fB\fB%+\fR\fR
.ad
.RS 12n
.rt  
Equivalent to \fB%%\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB%-\fR\fR
.ad
.RS 12n
.rt  
Previous job.
.RE

.sp
.LP
The shell learns immediately whenever a process changes state. It normally informs you whenever a job becomes blocked so that no further progress is possible, but only just before it prints a prompt. This is done so that it does not otherwise disturb your work. The notify option of the \fBset\fR command causes the shell to print these job change messages as soon as they occur.
.sp
.LP
When the \fBmonitor\fR option is on, each background job that completes triggers any trap set for \fBCHLD\fR.
.sp
.LP
When you try to leave the shell while jobs are running or stopped, you are warned that \fBYou have stopped(running) jobs.\fR You can use the \fBjobs\fR command to see what they are. If you immediately try to exit again, the shell does not warn you a second time, and the stopped jobs are terminated. When a login shell receives a \fBHUP\fR signal, it sends a \fBHUP\fR signal to each job that has not been disowned with the \fBdisown\fR built-in command.
.SS "Signals"
.sp
.LP
The \fBINT\fR and \fBQUIT\fR signals for an invoked command are ignored if the command is followed by \fB&\fR and the \fBmonitor\fR option is not active. Otherwise, signals have the values inherited by the shell from its parent. See the \fBtrap\fR built-in command.
.SS "Execution"
.sp
.LP
Each time a command is read, the substitutions are carried out. If the command name matches one of the ones in the \fBSpecial Built-in Commands\fR section of this manual page, it is executed within the current shell process. Next, the command name is checked to see if it matches a user defined function. If it does, the positional parameters are saved and then reset to the arguments of the function call. A function is also executed in the current shell process. When the function completes or issues a return, the positional parameter list is restored. For functions defined with the \fBfunction\fR \fBname\fR syntax, any trap set on \fBEXIT\fR within the function is executed. The exit value of a function is the value of the last command executed. If a command name is not a special built-in command or a user defined function, but it is one of the built-in commands, it is executed in the current shell process.
.sp
.LP
The shell variable \fBPATH\fR defines the search path for the directory containing the command. Alternative directory names are separated by a colon (\fB:\fR). The default path is \fB/bin:/usr/bin:\fR, specifying \fB/bin\fR, \fB/usr/bin\fR, and the current directory in that order. The current directory can be specified by two or more adjacent colons, or by a colon at the beginning or end of the path list. If the command name contains a slash (\fB/\fR), the search path is not used. Otherwise, each directory in the path is searched for an executable file of the specified name that is not a directory. If found, and if the shell determines that there is a built-in version of a command corresponding to a specified pathname, this built-in is invoked in the current process. If found, and this directory is also contained in the value of the \fBFPATH\fR variable, then this file is loaded into the current shell environment as if it were the argument to the . command except that only preset aliases are expanded, and a function of the specified name is executed as described in this manual page. If not found, and the file \fB\&.paths\fR is found, and this file contains a line of the form \fBFPATH=\fR\fIpath\fR where \fIpath\fR is an existing directory, and this directory contains a file of the specified name, then this file is loaded into the current shell environment as if it were the argument to the \fB\&. special\fR built-in command and a function of the specified name is executed. Otherwise, if found, a process is created and an attempt is made to execute the command using \fBexec\fR(2).
.sp
.LP
When an executable is found, the directory where it is found in is searched for a file named \fB\&.paths\fR. If this file is found and it contains a line of the form \fBBUILTIN_LIB=\fR\fIvalue\fR, the library named by \fIvalue\fR is searched for as if it were an option argument to \fBbuiltin -f\fR, and if it contains a built-in of the specified name this is executed instead of a command by this name. Otherwise, if this file is found and it contains a line of the form \fIname\fR\fB=\fR\fIvalue\fR in the first or second line, then the environment variable \fIname\fR is modified by prepending the directory specified by \fIvalue\fR to the directory list. If \fIvalue\fR is not an absolute directory, then it specifies a directory relative to the directory that the executable was found. If the environment variable \fIname\fR does not already exist it is added to the environment list for the specified command.
.sp
.LP
If the file has execute permission but is not an \fBa.out\fR file, it is assumed to be a file containing shell commands. A separate shell is spawned to read it. All non-exported variables are removed in this case. If the shell command file doesn't have read permission, and/or if the \fBsetuid\fR and \fBsetgid\fR bits are set on the file, then the shell executes an agent whose job it is to set up the permissions and execute the shell with the shell command file passed down as an open file. A parenthesized command is executed in a sub-shell without removing non-exported variables.
.SS "Command Re-entry"
.sp
.LP
The text of the last \fBHISTSIZE\fR (default 512) commands entered from a terminal device is saved in a history file. The file \fB$HOME/.sh_history\fR is used if the \fBHISTFILE\fR variable is not set or if the file it names is not writable. A shell can access the commands of all interactive shells which use the same named \fBHISTFILE\fR. The built-in command \fBhist\fR is used to list or edit a portion of this file. The portion of the file to be edited or listed can be selected by number or by giving the first character or characters of the command. A single command or range of commands can be specified. If you do not specify an editor program as an argument to \fBhist\fR then the value of the variable \fBHISTEDIT\fR is used. If \fBHISTEDIT\fR is unset, the obsolete variable \fBFCEDIT\fR is used. If \fBFCEDIT\fR is not defined, then \fB/bin/ed\fR is used. The edited commands are printed and executed again upon leaving the editor unless you quit without writing. The \fB-s\fR option (and in obsolete versions, the editor name \fB-\fR) is used to skip the editing phase and to re-execute the command. In this case a substitution parameter of the form \fIold\fR\fB=\fR\fInew\fRcan be used to modify the command before execution. For example, with the preset alias \fBr\fR, which is aliased to \fB\&'hist -s'\fR, typing \fB`r bad=good c'\fR re-executes the most recent command which starts with the letter \fBc\fR, replacing the first occurrence of the string bad with the string good. 
.SS "Inline Editing Options"
.sp
.LP
Normally, each command line entered from a terminal device is simply typed followed by a NEWLINE (RETURN or LINE FEED). If either the \fBemacs\fR, \fBgmacs\fR, or \fBvi\fR option is active, the user can edit the command line. To be in either of these edit modes set the corresponding option. An editing option is automatically selected each time the \fBVISUAL\fR or \fBEDITOR\fR variable is assigned a value ending in either of these option names.
.sp
.LP
The editing features require that the user's terminal accept RETURN as carriage return without line feed and that a SPACE must overwrite the current character on the screen.
.sp
.LP
Unless the \fBmultiline\fR option is on, the editing modes implement a concept where the user is looking through a window at the current line. The window width is the value of \fBCOLUMNS\fR if it is defined, otherwise \fB80\fR. If the window width is too small to display the prompt and leave at least 8 columns to enter input, the prompt is truncated from the left. If the line is longer than the window width minus two, a mark is displayed at the end of the window to notify the user. As the cursor moves and reaches the window boundaries the window is centered about the cursor. The mark is a \fB>\fR (\fB<, *\fR) if the line extends on the right , left, or both sides of the window.
.sp
.LP
The search commands in each edit mode provide access to the history file. Only strings are matched, not patterns, although a leading \fB^\fR in the string restricts the match to begin at the first character in the line.
.sp
.LP
Each of the edit modes has an operation to list the files or commands that match a partially entered word. When applied to the first word on the line, or the first word after a \fB;\fR, \fB|\fR, \fB&\fR, or \fB(\fR, and the word does not begin with \fB~\fR or contain a \fB/\fR, the list of aliases, functions, and executable commands defined by the \fBPATH\fR variable that could match the partial word is displayed. Otherwise, the list of files that match the specified word is displayed. If the partially entered word does not contain any file expansion characters, a \fB*\fR is appended before generating these lists. After displaying the generated list, the input line is redrawn. These operations are called command name listing and file name listing, respectively. There are additional operations, referred to as command name completion and file name completion, which compute the list of matching commands or files, but instead of printing the list, replace the current word with a complete or partial match. For file name completion, if the match is unique, a \fB/\fR is appended if the file is a directory and a space is appended if the file is not a directory. Otherwise, the longest common prefix for all the matching files replaces the word. For command name completion, only the portion of the file names after the last \fB/\fR are used to find the longest command prefix. If only a single name matches this prefix, then the word is replaced with the command name followed by a space. When using a \fBTAB\fR for completion that does not yield a unique match, a subsequent TAB provides a numbered list of matching alternatives. A specific selection can be made by entering the selection number followed by a TAB.
.SS "Key Bindings"
.sp
.LP
The \fBKEYBD\fR trap can be used to intercept keys as they are typed and change the characters that are actually seen by the shell. This trap is executed after each character (or sequence of characters when the first character is ESC) is entered while reading from a terminal.
.sp
.LP
The variable \fB\&.sh.edchar\fR contains the character or character sequence which generated the trap. Changing the value of \fB\&.sh.edchar\fR in the trap action causes the shell to behave as if the new value were entered from the keyboard rather than the original value. The variable \fB\&.sh.edcol\fR is set to the input column number of the cursor at the time of the input. The variable \fB\&.sh.edmode\fR is set to \fBESC\fR when in \fBvi\fR insert mode and is null otherwise. By prepending \fB${.sh.editmode}\fR to a value assigned to \fB\&.sh.edchar\fR it causes the shell to change to control mode if it is not already in this mode.
.sp
.LP
This trap is not invoked for characters entered as arguments to editing directives, or while reading input for a character search.
.SS "\fBemacs\fR Editing Mode"
.sp
.LP
This mode is entered by enabling either the \fBemacs\fR or \fBgmacs\fR option. The only difference between these two modes is the way they handle \fB^T\fR. To edit, the user moves the cursor to the point needing correction and then inserts or deletes characters or words as needed. All the editing commands are control characters or escape sequences. The notation for control characters is caret (\fB^\fR) followed by the character.
.sp
.LP
For example, \fB^F\fR is the notation for CTRL/F. This is entered by depressing \fBf\fR while holding down the CTRL (control) key. The SHIFT key is not depressed. (The notation \fB^?\fR indicates the DEL (delete) key.)
.sp
.LP
The notation for escape sequences is \fBM-\fR followed by a character. For example, \fBM-f\fR (pronounced \fBMeta f\fR) is entered by depressing ESC (\fBASCII 033\fR) followed by \fBf\fR. \fBM-F\fR is the notation for ESC followed by \fBF\fR.
.sp
.LP
All edit commands operate from any place on the line, not just at the beginning. The RETURN or the LINE FEED key is not entered after edit commands except when noted.
.sp
.ne 2
.mk
.na
\fB\fB^F\fR\fR
.ad
.RS 13n
.rt  
Move the cursor forward (right) one character.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-[C\fR\fR
.ad
.RS 13n
.rt  
Move the cursor forward (right) one character.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-f\fR\fR
.ad
.RS 13n
.rt  
Move the cursor forward one word. The \fBemacs\fR editor's idea of a word is a string of characters consisting of only letters, digits and underscores.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^B\fR\fR
.ad
.RS 13n
.rt  
Move the cursor backward (left) one character.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-[D\fR\fR
.ad
.RS 13n
.rt  
Move the cursor backward (left) one character.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-b\fR\fR
.ad
.RS 13n
.rt  
Move the cursor backward one word.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^A\fR\fR
.ad
.RS 13n
.rt  
Move the cursor to the beginning of the line.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-[H\fR\fR
.ad
.RS 13n
.rt  
Move the cursor to the beginning of the line.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^E\fR\fR
.ad
.RS 13n
.rt  
Move the cursor to the end of the line.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-[Y\fR\fR
.ad
.RS 13n
.rt  
Move the cursor to the end of line.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^]\fR\fIchar\fR\fR
.ad
.RS 13n
.rt  
Move the cursor forward to the character \fIchar\fR on the current line.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-^]\fR\fIchar\fR\fR
.ad
.RS 13n
.rt  
Move the cursor backwards to the character \fIchar\fR on the current line.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^X^X\fR\fR
.ad
.RS 13n
.rt  
Interchange the cursor and the mark.
.RE

.sp
.ne 2
.mk
.na
\fB\fIerase\fR\fR
.ad
.RS 13n
.rt  
Delete the previous character. The user-defined erase character is defined by the \fBstty\fR(1) command, and is usually \fB^H\fR or \fB#\fR. 
.RE

.sp
.ne 2
.mk
.na
\fB\fIlnext\fR\fR
.ad
.RS 13n
.rt  
Removes the next character's editing features. The user-defined literal next character is defined by the \fBstty\fR(1) command, or is \fB^V\fR if not defined. 
.RE

.sp
.ne 2
.mk
.na
\fB\fB^D\fR\fR
.ad
.RS 13n
.rt  
Delete the current character.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-d\fR\fR
.ad
.RS 13n
.rt  
Delete the current word.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-^H\fR\fR
.ad
.RS 13n
.rt  
MetaBACKSPACE. Delete the previous word.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-h\fR\fR
.ad
.RS 13n
.rt  
Delete the previous word.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-^?\fR\fR
.ad
.RS 13n
.rt  
MetaDEL. Delete the previous word. If your interrupt character is \fB^?\fR (DEL, the default), this command does not work.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^T\fR\fR
.ad
.RS 13n
.rt  
Transpose the current character with the previous character, and advance the cursor in \fBemacs\fR mode. Transpose two previous characters in \fBgmacs\fR mode.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^C\fR\fR
.ad
.RS 13n
.rt  
Capitalize the current character.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-c\fR\fR
.ad
.RS 13n
.rt  
Capitalize the current word.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-l\fR\fR
.ad
.RS 13n
.rt  
Change the current word to lower case.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^K\fR\fR
.ad
.RS 13n
.rt  
Delete from the cursor to the end of the line. If preceded by a numerical parameter whose value is less than the current cursor position, delete from specified position up to the cursor. If preceded by a numerical parameter whose value is greater than the current cursor position, then delete from cursor up to specified cursor position.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^W\fR\fR
.ad
.RS 13n
.rt  
Kill from the cursor to the mark.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-p\fR\fR
.ad
.RS 13n
.rt  
Push the region from the cursor to the mark on the stack.
.RE

.sp
.ne 2
.mk
.na
\fB\fIkill\fR\fR
.ad
.RS 13n
.rt  
Kill the entire current line. The user-defined kill character is defined by the \fBstty\fR(1) command, usually a \fB^G\fR or \fB@\fR. If two kill characters are entered in succession, all kill characters from then on cause a line feed. This is useful when using paper terminals.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^Y\fR\fR
.ad
.RS 13n
.rt  
Restore the last item removed from line. Yank the item back to the line.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^L\fR\fR
.ad
.RS 13n
.rt  
Line feed and print the current line.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-^L\fR\fR
.ad
.RS 13n
.rt  
Clear the screen.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^@\fR\fR
.ad
.RS 13n
.rt  
Null character. Set mark.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-\fR\fIspace\fR\fR
.ad
.RS 13n
.rt  
MetaSPACE. Set the mark.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^J\fR\fR
.ad
.RS 13n
.rt  
New line. Execute the current line.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^M\fR\fR
.ad
.RS 13n
.rt  
Return. Execute the current line.
.RE

.sp
.ne 2
.mk
.na
\fB\fBEOF\fR\fR
.ad
.RS 13n
.rt  
End-of-file character, normally \fB^D\fR, is processed as an \fBend-of-file\fR only if the current line is null.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^P\fR\fR
.ad
.RS 13n
.rt  
Fetch the previous command. Each time \fB^P\fR is entered the previous command back in time is accessed. Moves back one line when it is not on the first line of a multi-line command.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-[A\fR\fR
.ad
.RS 13n
.rt  
Equivalent to \fB^P\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-<\fR\fR
.ad
.RS 13n
.rt  
Fetch the least recent (oldest) history line.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM->\fR\fR
.ad
.RS 13n
.rt  
Fetch the most recent (youngest) history line.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^N\fR\fR
.ad
.RS 13n
.rt  
Fetch the next command line. Each time \fB^N\fR is entered the next command line forward in time is accessed.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-[B\fR\fR
.ad
.RS 13n
.rt  
Equivalent to \fB^N\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^R\fR\fIstring\fR\fR
.ad
.RS 13n
.rt  
Reverse search history for a previous command line containing \fIstring\fR. If a parameter of zero is specified, the search is forward. \fIstring\fR is terminated by a RETURN or NEWLINE. If string is preceded by a \fB^\fR, the matched line must begin with \fIstring\fR. If \fIstring\fR is omitted, then the next command line containing the most recent \fIstring\fR is accessed. In this case a parameter of zero reverses the direction of the search.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^O\fR\fR
.ad
.RS 13n
.rt  
Operate. Execute the current line and fetch the next line relative to current line from the history file.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-\fR\fIdigits\fR\fR
.ad
.RS 13n
.rt  
Escape. Define numeric parameter. The digits are taken as a parameter to the next command. The commands that accept a parameter are: \fB^F\fR, \fB^B\fR, \fBERASE\fR, \fB^C\fR, \fB^D\fR, \fB^K\fR, \fB^R\fR, \fB^P\fR, \fB^N\fR, \fB^]\fR, \fBM-.\fR, \fBM-\fR, \fBM-^]\fR, \fBM-_\fR, \fBM-=\fR, \fBM-b\fR, \fBM-c\fR, \fBM-d\fR, \fBM-f\fR, \fBM-h\fR, \fBM-l\fR, and \fBM-^H\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-\fR\fIletter\fR\fR
.ad
.RS 13n
.rt  
Soft-key. Search the alias list for an alias by the name \fIletter\fR. If an alias of \fIletter\fR is defined, insert its value on the input queue. \fIletter\fR must not be one of the metafunctions in this section.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-[\fR\fIletter\fR\fR
.ad
.RS 13n
.rt  
Soft key. Search the alias list for an alias by the name \fIletter\fR. If an alias of this name is defined, insert its value on the input queue. This can be used to program function keys on many terminals.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-.\fR\fR
.ad
.RS 13n
.rt  
The last word of the previous command is inserted on the line. If preceded by a numeric parameter, the value of this parameter determines which word to insert rather than the last word.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-_\fR\fR
.ad
.RS 13n
.rt  
Same as \fBM-.\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-*\fR\fR
.ad
.RS 13n
.rt  
Attempt filename generation on the current word. As asterisk is appended if the word does not match any file or contain any special pattern characters.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-\fRESC\fR
.ad
.RS 13n
.rt  
Command or file name completion as described in this manual page.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^I\fRTAB\fR
.ad
.RS 13n
.rt  
Attempts command or file name completion as described in this manual page. If a partial completion occurs, repeating this behaves as if \fBM-=\fR were entered. If no match is found or entered after SPACE, a TAB is inserted.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-=\fR\fR
.ad
.RS 13n
.rt  
If not preceded by a numeric parameter, generates the list of matching commands or file names as described in this manual page. Otherwise, the word under the cursor is replaced by the item corresponding to the value of the numeric parameter from the most recently generated command or file list. If the cursor is not on a word, the word is inserted instead. 
.RE

.sp
.ne 2
.mk
.na
\fB\fB^U\fR\fR
.ad
.RS 13n
.rt  
Multiply parameter of next command by \fB4\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\e\fR\fR
.ad
.RS 13n
.rt  
Escape the next character. Editing characters, the user's erase, kill and interrupt (normally \fB^?\fR) characters can be entered in a command line or in a search string if preceded by a \fB\e\fR\&. The \fB\e\fR removes the next character's editing features, if any.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-^V\fR\fR
.ad
.RS 13n
.rt  
Display the version of the shell.
.RE

.sp
.ne 2
.mk
.na
\fB\fBM-#\fR\fR
.ad
.RS 13n
.rt  
If the line does not begin with a \fB#\fR, a \fB#\fR is inserted at the beginning of the line and after each NEWLINE, and the line is entered. This causes a comment to be inserted in the history file. If the line begins with a \fB#\fR, the \fB#\fR is deleted and one \fB#\fR after each NEWLINE is also deleted.
.RE

.SS "\fBvi\fR Editing Mode"
.sp
.LP
There are two typing modes. Initially, when you enter a command you are in the input mode. To edit, the user enters control mode by typing ESC (033) and moves the cursor to the point needing correction and then inserts or deletes characters or words as needed. Most control commands accept an optional repeat \fIcount\fR prior to the command. 
.sp
.LP
When in vi mode on most systems, canonical processing is initially enabled and the command is echoed again if the speed is 1200 baud or greater and it contains any control characters or less than one second has elapsed since the prompt was printed. The ESC character terminates canonical processing for the remainder of the command and the user can then modify the command line. This scheme has the advantages of canonical processing with the type-ahead echoing of raw mode.
.sp
.LP
If the option \fBviraw\fR is also set, the terminal is always have canonical processing disabled. This mode is implicit for systems that do not support two alternate end of line delimiters, and might be helpful for certain terminals. 
.SS "Input Edit Commands"
.sp
.LP
By default the editor is in input mode.
.sp
.LP
The following input edit commands are supported:
.sp
.ne 2
.mk
.na
\fBERASE\fR
.ad
.RS 10n
.rt  
User defined erase character as defined by the \fBstty\fR command, usually \fB^H\fR or \fB#\fR. Delete previous character.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^W\fR\fR
.ad
.RS 10n
.rt  
Delete the previous blank separated word. On some systems the \fBviraw\fR option might be required for this to work.
.RE

.sp
.ne 2
.mk
.na
\fBEOF\fR
.ad
.RS 10n
.rt  
As the first character of the line causes the shell to terminate unless the \fBignoreeof\fR option is set. Otherwise this character is ignored.
.RE

.sp
.ne 2
.mk
.na
\fB\fIlnext\fR\fR
.ad
.RS 10n
.rt  
User defined literal next character as defined by the \fBstty\fR(1) or \fB^V\fR if not defined. Removes the next character's editing features, if any. On some systems the \fBviraw\fR option might be required for this to work.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\e\fR\fR
.ad
.RS 10n
.rt  
Escape the next ERASE or KILL character.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^I\fR TAB\fR
.ad
.RS 10n
.rt  
Attempts command or file name completion as described in this manual page and returns to input mode. If a partial completion occurs, repeating this behaves as if \fB=\fR were entered from control mode. If no match is found or entered after SPACE, a TAB is inserted.
.RE

.SS "Motion Edit Commands"
.sp
.LP
The motion edit commands move the cursor.
.sp
.LP
The following motion edit commands are supported:
.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]l\fR\fR
.ad
.RS 13n
.rt  
Move the cursor forward (right) one character.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB][C\fR\fR
.ad
.RS 13n
.rt  
Move the cursor forward (right) one character.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]w\fR\fR
.ad
.RS 13n
.rt  
Move the cursor forward one alphanumeric word.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]W\fR\fR
.ad
.RS 13n
.rt  
Move the cursor to the beginning of the next word that follows a blank.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]e\fR\fR
.ad
.RS 13n
.rt  
Move the cursor to the end of the word.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]E\fR\fR
.ad
.RS 13n
.rt  
Move the cursor to the end of the current blank delimited word.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]h\fR\fR
.ad
.RS 13n
.rt  
Move the cursor backward (left) one character.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB][D\fR\fR
.ad
.RS 13n
.rt  
Move the cursor backward (left) one character.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]b\fR\fR
.ad
.RS 13n
.rt  
Move the cursor backward one word.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]B\fR\fR
.ad
.RS 13n
.rt  
Move the cursor to the preceding blank separated word.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]|\fR\fR
.ad
.RS 13n
.rt  
Move the cursor to column \fIcount\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]f\fR\fIc\fR\fR
.ad
.RS 13n
.rt  
Find the next character \fIc\fR in the current line.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]F\fR\fIc\fR\fR
.ad
.RS 13n
.rt  
Find the previous character \fIc\fR in the current line.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]t\fR\fIC\fR\fR
.ad
.RS 13n
.rt  
Equivalent to \fBf\fR followed by \fBh\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]T\fR\fIc\fR\fR
.ad
.RS 13n
.rt  
Equivalent to \fBF\fR followed by \fBl\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB];\fR\fR
.ad
.RS 13n
.rt  
Repeat \fIcount\fR times the last single character find command: \fBf\fR, \fBF\fR, \fBt,\fR or \fBT\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB],\fR\fR
.ad
.RS 13n
.rt  
Reverse the last single character find command \fIcount\fR times.
.RE

.sp
.ne 2
.mk
.na
\fB\fB0\fR\fR
.ad
.RS 13n
.rt  
Move the cursor to the start of line.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^\fR\fR
.ad
.RS 13n
.rt  
Move the cursor to start of line.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[H\fR\fR
.ad
.RS 13n
.rt  
Move the cursor to the first non-blank character in the line.
.RE

.sp
.ne 2
.mk
.na
\fB\fB$\fR\fR
.ad
.RS 13n
.rt  
Move the cursor to the end of the line.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[Y\fR\fR
.ad
.RS 13n
.rt  
Move the cursor to the end of the line.
.RE

.sp
.ne 2
.mk
.na
\fB\fB%\fR\fR
.ad
.RS 13n
.rt  
Moves to balancing \fB(\fR, \fB)\fR, \fB{\fR, \fB}\fR, \fB[\fR, or \fB]\fR. If cursor is not on one of the characters described in this section, the remainder of the line is searched for the first occurrence of one of the characters first.
.RE

.SS "Search Edit Commands"
.sp
.LP
The search edit commands access your command history.
.sp
.LP
The following search edit commands are supported:
.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]k\fR\fR
.ad
.RS 13n
.rt  
Fetch the previous command. Each time \fBk\fR is entered, the previous command back in time is accessed.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]-\fR\fR
.ad
.RS 13n
.rt  
Fetch the previous command. Each time \fBk\fR is entered, the previous command back in time is accessed.
.sp
Equivalent to \fBk\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB][A\fR\fR
.ad
.RS 13n
.rt  
Fetch the previous command. Each time \fBk\fR is entered, the previous command back in time is accessed.
.sp
Equivalent to \fBk\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]j\fR\fR
.ad
.RS 13n
.rt  
Fetch the next command. Each time \fBj\fR is entered, the next command forward in time is accessed.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]+\fR\fR
.ad
.RS 13n
.rt  
Fetch the next command. Each time \fBj\fR is entered, the next command forward in time is accessed.
.sp
Equivalent to \fBj\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB][B\fR\fR
.ad
.RS 13n
.rt  
Fetch the next command. Each time \fBj\fR is entered, the next command forward in time is accessed.
.sp
Equivalent to \fBj\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]G\fR\fR
.ad
.RS 13n
.rt  
Fetch command number \fIcount\fR. The default is the least recent history command.
.RE

.sp
.ne 2
.mk
.na
\fB\fB/\fR\fIstring\fR\fR
.ad
.RS 13n
.rt  
Search backward through history for a previous command containing \fIstring\fR. \fIstring\fR is terminated by a RETURN or NEWLINE. If string is preceded by a \fB^\fR, the matched line must begin with \fIstring\fR. If \fIstring\fR is null, the previous string is used.
.RE

.sp
.ne 2
.mk
.na
\fB\fB?\fR\fIstring\fR\fR
.ad
.RS 13n
.rt  
Search forward through history for a previous command containing \fIstring\fR. \fIstring\fR is terminated by a RETURN or NEWLINE. If string is preceded by a \fB^\fR, the matched line must begin with \fIstring\fR. If \fIstring\fR is null, the previous string is used.
.sp
Same as \fI/\fR except that search is in the forward direction.
.RE

.sp
.ne 2
.mk
.na
\fB\fBn\fR\fR
.ad
.RS 13n
.rt  
Search in the backwards direction for the next match of the last pattern to \fI/\fR or \fI?\fR commands.
.RE

.sp
.ne 2
.mk
.na
\fB\fBN\fR\fR
.ad
.RS 13n
.rt  
Search in the forward direction for next match of the last pattern to \fI/\fR or \fI?\fR.
.RE

.SS "Text Modification Edit Commands"
.sp
.LP
The following commands modify the line:
.sp
.ne 2
.mk
.na
\fB\fBa\fR\fR
.ad
.RS 19n
.rt  
Enter input mode and enter text after the current character.
.RE

.sp
.ne 2
.mk
.na
\fB\fBA\fR\fR
.ad
.RS 19n
.rt  
Append text to the end of the line. Equivalent to \fB$a\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]c\fR\fImotion\fR\fR
.ad
.br
.na
\fB\fBc[\fR\fIcount\fR\fB]\fR\fImotion\fR\fR
.ad
.RS 19n
.rt  
Delete current character through the character that \fImotion\fR would move the cursor to and enter input mode. If \fImotion\fR is \fBc\fR, the entire line is deleted and input mode entered.
.RE

.sp
.ne 2
.mk
.na
\fB\fBC\fR\fR
.ad
.RS 19n
.rt  
Delete the current character through the end of line and enter input mode. Equivalent to \fBc$\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBS\fR\fR
.ad
.RS 19n
.rt  
Equivalent to \fBcc\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]s\fR\fR
.ad
.RS 19n
.rt  
Replace characters under the cursor in input mode.
.RE

.sp
.ne 2
.mk
.na
\fB\fBD[\fR\fIcount\fR\fB]d\fR\fImotion\fR\fR
.ad
.RS 19n
.rt  
Delete the current character through the end of line. Equivalent to d$.
.RE

.sp
.ne 2
.mk
.na
\fB\fBd[\fR\fIcount\fR\fB]\fR\fImotion\fR\fR
.ad
.RS 19n
.rt  
Delete current character through the character that \fImotion\fR would move to. If \fImotion\fR is d , the entire line is deleted.
.RE

.sp
.ne 2
.mk
.na
\fB\fBi\fR\fR
.ad
.RS 19n
.rt  
Enter input mode and insert text before the current character.
.RE

.sp
.ne 2
.mk
.na
\fB\fBI\fR\fR
.ad
.RS 19n
.rt  
Insert text before the beginning of the line. Equivalent to \fB0i\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]P\fR\fR
.ad
.RS 19n
.rt  
Place the previous text modification before the cursor.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]p\fR\fR
.ad
.RS 19n
.rt  
Place the previous text modification after the cursor.
.RE

.sp
.ne 2
.mk
.na
\fB\fBR\fR\fR
.ad
.RS 19n
.rt  
Enter input mode and replace characters on the screen with characters you type overlay fashion.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]r\fR\fIc\fR\fR
.ad
.RS 19n
.rt  
Replace the \fIcount\fR characters starting at the current cursor position with \fIc\fR, and advance the cursor.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]x\fR\fR
.ad
.RS 19n
.rt  
Delete current character.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fIcount\fR]X\fR\fR
.ad
.RS 19n
.rt  
Delete preceding character.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fIcount\fR].\fR\fR
.ad
.RS 19n
.rt  
Repeat the previous text modification command.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fIcount\fR]~\fR\fR
.ad
.RS 19n
.rt  
Invert the case of the \fIcount\fR characters starting at the current cursor position and advance the cursor.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fIcount\fR]_\fR\fR
.ad
.RS 19n
.rt  
Causes the \fIcount\fR word of the previous command to be appended and input mode entered. The last word is used if \fIcount\fR is omitted.
.RE

.sp
.ne 2
.mk
.na
\fB\fB*\fR\fR
.ad
.RS 19n
.rt  
Causes an \fB*\fR to be appended to the current word and file name generation attempted. If no match is found, it rings the bell. Otherwise, the word is replaced by the matching pattern and input mode is entered.
.RE

.sp
.ne 2
.mk
.na
\fB\fB\e\fR\fR
.ad
.RS 19n
.rt  
Command or file name completion as described in this manual page.
.RE

.SS "Other Edit Commands"
.sp
.LP
The following miscellaneous edit commands are supported: 
.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]y\fR\fImotion\fR\fR
.ad
.br
.na
\fB\fBy[\fR\fIcount\fR\fB]\fR\fImotion\fR\fR
.ad
.RS 18n
.rt  
Yank the current character through the character to which \fImotion\fR would move the cursor. Put the yanked characters in the delete buffer. The text and cursor position are unchanged.
.RE

.sp
.ne 2
.mk
.na
\fB\fByy\fR\fR
.ad
.RS 18n
.rt  
Yank the current line.
.RE

.sp
.ne 2
.mk
.na
\fB\fBY\fR\fR
.ad
.RS 18n
.rt  
Yank the current line from the current cursor location to the end of the line. Equivalent to \fBy$\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBu\fR\fR
.ad
.RS 18n
.rt  
Undo the last text modifying command.
.RE

.sp
.ne 2
.mk
.na
\fB\fBU\fR\fR
.ad
.RS 18n
.rt  
Undo all the text modifying commands performed on current line.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]V\fR\fR
.ad
.RS 18n
.rt  
Return the command :
.sp
.in +2
.nf
hist -e ${VISUAL:-${EDITOR:-vi}} \fIcount\fR
.fi
.in -2
.sp

in the input buffer. If \fIcount\fR is omitted, the current line is used.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^L\fR\fR
.ad
.RS 18n
.rt  
Line feed and print the current line. This command only works in control mode.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^J\fR\fR
.ad
.RS 18n
.rt  
New line. Execute the current line, regardless of mode.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^M\fR\fR
.ad
.RS 18n
.rt  
Return. Execute the current line, regardless of mode.
.RE

.sp
.ne 2
.mk
.na
\fB\fB#\fR\fR
.ad
.RS 18n
.rt  
If the first character of the command is a \fB#\fR , delete this \fB#\fR and each \fB#\fR that follows a NEWLINE.
.sp
Otherwise, send the line after inserting a \fB#\fR in front of each line in the command. 
.sp
This is command is useful for causing the current line to be inserted in the history as a comment and un-commenting previously commented commands in the history file.
.RE

.sp
.ne 2
.mk
.na
\fB\fB[\fR\fIcount\fR\fB]=\fR\fR
.ad
.RS 18n
.rt  
If \fIcount\fR is not specified, generate the list of matching commands or file names as described in this manual page.
.sp
Otherwise, replace the word at the current cursor location with the \fIcount\fR item from the most recently generated command or file list. If the cursor is not on a word, it is inserted after the current cursor location.
.RE

.sp
.ne 2
.mk
.na
\fB\fB@\fR\fIletter\fR\fR
.ad
.RS 18n
.rt  
Search your alias list for an alias by the name \fIletter\fR. If an alias of this name is defined, insert its value on the input queue for processing.
.RE

.sp
.ne 2
.mk
.na
\fB\fB^V\fR\fR
.ad
.RS 18n
.rt  
Display version of the shell.
.RE

.SS "Built-in Commands"
.sp
.LP
The following simple-commands are executed in the shell process. Input and output redirection is permitted. Unless otherwise indicated, the output is written on file descriptor \fB1\fR and the exit status, when there is no syntax error, is \fB0\fR. Except for \fB:\fR, \fBtrue\fR, \fBfalse\fR, \fBecho\fR, \fBnewgrp\fR, and \fBlogin\fR, all built-in commands accept \fB--\fR to indicate the end of options. They also interpret the option \fB--man\fR as a request to display the manual page onto standard error and \fB-?\fR as a help request which prints a usage message on standard error.
.sp
.LP
Commands that are preceded by one or two \fB++\fR symbols are special built-in commands and are treated specially in the following ways:
.RS +4
.TP
1.
Variable assignment lists preceding the command remain in effect when the command completes.
.RE
.RS +4
.TP
2.
I/O redirections are processed after variable assignments.
.RE
.RS +4
.TP
3.
Errors cause a script that contains them to abort.
.RE
.RS +4
.TP
4.
They are not valid function names.
.RE
.RS +4
.TP
5.
Words following a command preceded by \fB++\fR that are in the format of a variable assignment are expanded with the same rules as a variable assignment. This means that tilde substitution is performed after the \fB=\fR sign and field splitting and file name generation are not performed.
.RE
.sp
.ne 2
.mk
.na
\fB\fB+ : [\fR\fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
The command only expands parameters.
.RE

.sp
.ne 2
.mk
.na
\fB\fB+ .\fR \fIname\fR \fB[\fR\fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
If \fIname\fR is a function defined with the \fBfunction\fR \fBname\fR reserved word syntax, the function is executed in the current environment (as if it had been defined with the \fIname()\fR syntax.) Otherwise if \fIname\fR refers to a file, the file is read in its entirety and the commands are executed in the current shell environment. The search path specified by PATH is used to find the directory containing the file. If any arguments \fIarg\fR are specified, they become the positional parameters while processing the . command and the original positional parameters are restored upon completion. Otherwise the positional parameters are unchanged. The exit status is the exit status of the last command executed.
.RE

.sp
.ne 2
.mk
.na
\fB\fB++ alias [\fR\fB-ptx\fR\fB] [\fR\fIname\fR\fB[ =\fR\fIvalue\fR\fB]] ...\fR\fR
.ad
.sp .6
.RS 4n
\fBalias\fR with no arguments prints the list of aliases in the form \fIname\fR\fB=\fR\fIvalue\fR on standard output. The \fB-p\fR option causes the word alias to be inserted before each one. When one or more arguments are specified, an \fIalias\fR is defined for each \fIname\fR whose \fIvalue\fR is specified. A trailing space in \fIvalue\fR causes the next word to be checked for alias substitution. The obsolete \fB-t\fR option is used to set and list tracked aliases. The value of a tracked alias is the full pathname corresponding to the specified \fIname\fR. The value becomes undefined when the value of \fBPATH\fR is reset but the alias remains tracked. Without the \fB-t\fR option, for each \fIname\fR in the argument list for which no \fIvalue\fR is specified, the name and value of the alias is printed. The obsolete -x option has no effect. The exit status is \fBnon-zero\fR if a \fIname\fR is specified, but no value, and no alias has been defined for the \fIname\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBbg [\fR \fIjob\fR\fB\&...]\fR\fR
.ad
.sp .6
.RS 4n
This command is only on systems that support job control. Puts each specified \fIjob\fR into the background. The current job is put in the background if \fIjob\fR is not specified. See the \fBJobs\fR section of this manual page for a description of the format of \fIjob\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB+ break [\fR\fIn\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Exit from the enclosing \fBfor\fR, \fBwhile\fR, \fBuntil\fR, or \fBselect\fR loop, if any. If \fIn\fR is specified, then break \fIn\fR levels. 
.RE

.sp
.ne 2
.mk
.na
\fB\fBbuiltin [\fR\fB-ds\fR \fB] [\fR\fB-f\fR \fIfile\fR\fB] [\fR\fIname ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
If \fIname\fR is not specified, and no \fB-f\fR option is specified, the built-ins are printed on standard output. The \fB-s\fR option prints only the special built-ins. Otherwise, each \fIname\fR represents the pathname whose basename is the name of the built-in. The entry point function name is determined by prepending \fIb\fR to the built-in name. The ISO C/C++ prototype is \fBb\fR\fImycommand(int argc, char *argv[], void *context)\fR for the built-in command \fImycommand\fR where \fIargv\fR is an array of \fIargc\fR elements and \fIcontext\fR is an optional pointer to a \fBShell_t\fR structure as described in \fB<ast/shell.h>\fR Special built-ins cannot be bound to a pathname or deleted. The \fB-d\fR option deletes each of the specified built-ins. On systems that support dynamic loading, the \fB-f\fR option names a shared library containing the code for built-ins. The shared library prefix and/or suffix, which depend on the system, can be omitted. Once a library is loaded, its symbols become available for subsequent invocations of \fBbuiltin\fR. Multiple libraries can be specified with separate invocations of the \fBbuiltin\fR command. Libraries are searched in the reverse order in which they are specified. When a library is loaded, it looks for a function in the library whose name is \fBlib_init()\fR and invokes this function with an argument of \fB0\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBcd\fR \fB[\fR\fB-LP\fR\fB] [\fR\fIarg\fR\fB]\fR\fR
.ad
.br
.na
\fB\fBcd\fR \fB[\fR\fB-LP\fR\fB]\fR \fIold\fR \fInew\fR\fR
.ad
.sp .6
.RS 4n
This command has two forms. 
.sp
In the first form it changes the current directory to \fIarg\fR. If \fIarg\fR is a \fB-\fR, the directory is changed to the previous directory. The shell variable \fBHOME\fR is the default \fIarg\fR. The variable \fBPWD\fR is set to the current directory. The shell variable \fBCDPATH\fR defines the search path for the directory containing \fIarg\fR. Alternative directory names are separated by a colon (\fB:\fR). The default path is \fBNULL\fR (specifying the current directory). The current directory is specified by a null path name, which can appear immediately after the equal sign or between the colon delimiters anywhere else in the path list. If \fIarg\fR begins with a \fB/\fR, the search path is not used. Otherwise, each directory in the path is searched for \fIarg\fR. 
.sp
The second form of \fBcd\fR substitutes the string \fInew\fR for the string \fIold\fR in the current directory name, \fBPWD\fR, and tries to change to this new directory. By default, symbolic link names are treated literally when finding the directory name. This is equivalent to the \fB-L\fR option. The \fB-P\fR option causes symbolic links to be resolved when determining the directory. The last instance of \fB-L\fR or \fB-P\fR on the command line determines which method is used. The \fBcd\fR command cannot be executed by \fBrksh\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBcommand\fR \fB[\fR\fB-pvVx\fR\fB]\fR \fIname\fR \fB[\fR\fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Without the \fB-v\fR or \fB-V\fR options, executes \fIname\fR with the arguments specified by \fIarg\fR. 
.sp
The \fB-p\fR option causes a default path to be searched rather than the one defined by the value of \fBPATH\fR. Functions are not searched when finding \fIname\fR. In addition, if \fIname\fR refers to a special built-in, none of the special properties associated with the leading daggers are honored. For example, the predefined alias \fBredirect='command exec'\fR prevents a script from terminating when an invalid redirection is specified. 
.sp
With the \fB-x\fR option, if command execution would result in a failure because there are too many arguments, \fBerrno E2BIG\fR, the shell invokes command \fIname\fR multiple times with a subset of the arguments on each invocation. Arguments that occur prior to the first word that expands to multiple arguments and after the last word that expands to multiple arguments are passed on each invocation. The exit status is the maximum invocation exit status. 
.sp
With the \fB-v\fR option, \fBcommand\fR is equivalent to the built-in \fBwhence\fR command described in this section. The \fB-V\fR option causes \fBcommand\fR to act like \fBwhence -v\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB+continue\fR \fB[\fR\fIn\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Resumes the next iteration of the enclosing \fBfor\fR, \fBwhile\fR, \fBuntil\fR, or \fBselect\fR loop. If \fIn\fR is specified, then resume at the \fIn\fRth enclosing loop.
.RE

.sp
.ne 2
.mk
.na
\fB\fBdisown\fR \fB[\fR\fIjob...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Causes the shell not to send a \fBHUP\fR signal to each specified \fIjob\fR, or all active jobs if \fIjob\fR is omitted, when a login shell terminates.
.RE

.sp
.ne 2
.mk
.na
\fB\fBecho\fR \fB[\fR\fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
When the first \fIarg\fR does not begin with a \fB-\fR, and none of the arguments contain a backslash (\fB\e\fR), prints each of its arguments separated by a SPACE and terminated by a NEWLINE. Otherwise, the behavior of \fBecho\fR is system dependent and \fBprint\fR or \fBprintf\fR described in this section should be used. See \fBecho\fR(1) for usage and description.
.RE

.sp
.ne 2
.mk
.na
\fB\fB+eval\fR \fB[\fR\fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
The arguments are read as input to the shell and the resulting commands are executed.
.RE

.sp
.ne 2
.mk
.na
\fB\fB+exec\fR [\fB-c\fR] [\fB-a\fR \fIname ...\fR] \fB[\fR\fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
If \fIarg\fR is specified, the command specified by the arguments is executed in place of this shell without creating a new process. The \fB-c\fR option causes the environment to be cleared before applying variable assignments associated with the exec invocation. The \fB-a\fR option causes \fIname\fR rather than the first \fIarg\fR, to become \fBargv[0]\fR for the new process. Input and output arguments can appear and affect the current process. If \fIarg\fR is not specified, the effect of this command is to modify file descriptors as prescribed by the input/output redirection list. In this case, any file descriptor numbers greater than \fB2\fR that are opened with this mechanism are closed when invoking another program.
.RE

.sp
.ne 2
.mk
.na
\fB\fB+exit\fR \fB[\fR\fIn\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Causes the shell to exit with the exit status specified by \fIn\fR. The value is the least significant 8 bits of the specified status. If \fIn\fR is omitted, then the exit status is that of the last command executed. An end-of-file also causes the shell to exit except for a shell which has the \fBignoreeof\fR option turned on. See \fBset\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB++export\fR \fB[\fR\fB-p\fR\fB]\fR \fB[\fR\fIname\fR\fB[=\fR\fIvalue\fR\fB]] ...\fR\fR
.ad
.sp .6
.RS 4n
If \fIname\fR is not specified, the names and values of each variable with the export attribute are printed with the values quoted in a manner that allows them to be re-entered. The \fB-p\fR option causes the word export to be inserted before each one. Otherwise, the specified \fIname\fRs are marked for automatic export to the environment of subsequently-executed commands.
.RE

.sp
.ne 2
.mk
.na
\fB\fBfalse\fR\fR
.ad
.sp .6
.RS 4n
Does nothing, and exits \fB1\fR. Used with \fBuntil\fR for infinite loops.
.RE

.sp
.ne 2
.mk
.na
\fB\fBfg\fR \fB[\fR\fIjob ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
This command is only on systems that support job control. Each \fIjob\fR specified is brought to the foreground and waited for in the specified order. Otherwise, the current job is brought into the foreground. See \fBJobs\fR for a description of the format of \fIjob\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBgetconf\fR \fB[\fR\fIname\fR \fB[\fR\fIpathname\fR\fB]]\fR\fR
.ad
.sp .6
.RS 4n
Prints the current value of the configuration parameter specified by \fIname\fR. The configuration parameters are defined by the IEEE POSIX 1003.1 and IEEE POSIX 1003.2 standards. See \fBpathconf\fR(2) and \fBsysconf\fR(3C).
.sp
The \fIpathname\fR argument is required for parameters whose value depends on the location in the file system. If no arguments are specified, \fBgetconf\fR prints the names and values of the current configuration parameters. The pathname \fB/\fR is used for each of the parameters that requires \fIpathname\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBgetopts\fR \fB[\fR \fB-a\fR \fIname\fR\fB]\fR \fIoptstring\fR \fIvname\fR \fB[\fR\fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Checks \fIarg\fR for legal options. If \fIarg\fR is omitted, the positional parameters are used. An option argument begins with a \fB+\fR or a \fB-\fR. An option that does not begin with \fB+\fR or \fB-\fR or the argument \fB--\fR ends the options. Options beginning with \fB+\fR are only recognized when \fIoptstring\fR begins with a \fB+\fR. \fIoptstring\fR contains the letters that \fBgetopts\fR recognizes. If a letter is followed by a \fB:\fR, that option is expected to have an argument. The options can be separated from the argument by blanks. The option \fB-?\fRcauses \fBgetopts\fR to generate a usage message on standard error. The \fB-a\fR option can be used to specify the name to use for the usage message, which defaults to $0. \fBgetopts\fR places the next option letter it finds inside variable \fIvname\fR each time it is invoked. The option letter is prepended with a \fB+\fR when \fIarg\fR begins with a \fB+\fR. The index of the next \fIarg\fR is stored in \fBOPTIND\fR. The option argument, if any, gets stored in \fBOPTARG\fR. A leading : in \fIoptstring\fR causes \fBgetopts\fR to store the letter of an invalid option in \fBOPTARG\fR, and to set \fIvname\fR to \fB?\fR for an unknown option and to: when a required option argument is missing. Otherwise, \fBgetopts\fR prints an error message. The exit status is \fBnon-zero\fR when there are no more options. There is no way to specify any of the options \fB:\fR, \fB+\fR, \fB-\fR, \fB?\fR, \fB[\fR, and \fB]\fR. The option \fB#\fR can only be specified as the first option.
.RE

.sp
.ne 2
.mk
.na
\fB\fBhist\fR \fB[\fR \fB-e\fR \fIename\fR\fB]\fR\fB[\fR\fB-nlr\fR\fB]\fR \fB[\fR \fIfirst\fR\fB[\fR\fIlast\fR \fB] ]\fR\fR
.ad
.br
.na
\fB\fR
.ad
.br
.na
\fB\fBhist\fR \fB-s\fR \fB[\fR \fIold\fR\fB=\fR\fInew\fR \fB] [\fR \fIcommand\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
In the first form, a range of commands from \fIfirst\fR to \fIlast\fR is selected from the last \fBHISTSIZE\fR commands that were typed at the terminal. The arguments \fIfirst\fR and \fIlast\fR can be specified as a number or as a string. A string is used to locate the most recent command starting with the specified string. A negative number is used as an offset to the current command number. If the -l option is selected, the commands are listed on standard output. Otherwise, the editor program \fIename\fR is invoked on a file containing these keyboard commands. If \fIename\fR is not supplied, then the value of the variable \fBHISTEDIT\fR is used. If \fBHISTEDIT\fR is not set, then \fBFCEDIT\fR (default \fB/bin/ed\fR) is used as the editor. When editing is complete, the edited command(s) is executed if the changes have been saved. If \fIlast\fR is not specified, then it is set to \fIfirst\fR. If \fIfirst\fR is not specified, the default is the previous command for editing and \fB-16\fR for listing. The option \fB-r\fR reverses the order of the commands and the option \fB-n\fR suppresses command numbers when listing. In the second form, \fIcommand\fR is interpreted as \fIfirst\fR described in this section and defaults to the last command executed. The resulting command is executed after the optional substitution \fIold\fR\fB=\fR\fInew\fR is performed.
.RE

.sp
.ne 2
.mk
.na
\fB\fBjobs\fR \fB-lnp\fR \fB[\fR\fIjob ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Lists information about each specified job, or all active jobs if \fIjob\fR is omitted. The \fB-l\fR option lists process ids in addition to the normal information. The \fB-n\fR option only displays jobs that have stopped or exited since last notified. The \fB-p\fR option causes only the process group to be listed. See \fBJobs\fR for a description of the format of \fIjob\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBkill\fR \fB[\fR\fB-s\fR \fIsigname\fR\fB]\fR \fIjob ...\fR\fR
.ad
.br
.na
\fB\fBkill\fR \fB[\fR\fB-n\fR \fIsignum\fR\fB]\fR \fIjob ...\fR\fR
.ad
.br
.na
\fB\fBkill\fR \fB-l\fR \fB[\fR\fIsig ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Sends either the \fBTERM\fR (terminate) signal or the specified signal to the specified jobs or processes. Signals are either specified by number with the \fB-n\fR option or by name with the \fB-s\fR option (as specified in \fB<signal.h\fR>, stripped of the prefix `\fBSIG\fR with the exception that \fBSIGCLD\fR is named \fBCHLD\fR). For backward compatibility, the \fBn\fR and \fBs\fR can be omitted and the number or name placed immediately after the \fB-\fR. If the signal being sent is \fBTERM\fR (terminate) or \fBHUP\fR (hang up), then the job or process is sent a \fBCONT\fR (continue) signal if it is stopped. The argument \fIjob\fR can be the process id of a process that is not a member of one of the active jobs. See \fBJobs\fR for a description of the format of \fIjob\fR. In the third form, \fBkill -l\fR, if \fIsig\fR is not specified, the signal names are listed. Otherwise, for each \fIsig\fR that is a name, the corresponding signal number is listed. For each \fIsig\fR that is a number, the signal name corresponding to the least significant 8 bits of \fIsig\fR is listed.
.RE

.sp
.ne 2
.mk
.na
\fB\fBlet\fR \fB[\fR\fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Each \fIarg\fR is a separate arithmetic expression to be evaluated. See the \fBArithmetic Evaluation\fR section of this manual page for a description of arithmetic expression evaluation. The exit status is \fB0\fR if the value of the last expression is \fBnon-zero\fR, and \fB1\fR otherwise.
.RE

.sp
.ne 2
.mk
.na
\fB\fB+newgrp\fR \fB[\fR\fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Equivalent to \fBexec\fR \fB/bin/newgrp\fR \fIarg ...\fR
.RE

.sp
.ne 2
.mk
.na
\fB\fBprint\fR [\fB-Renprs\fR] \fB[\fR \fB-u\fR \fIunit\fR\fB] [\fR \fB-f\fR \fIformat\fR \fB] [\fR \fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
With no options or with option \fB-\fR or \fB--\fR, each \fIarg\fR is printed on standard output. The \fB-f\fR option causes the arguments to be printed as described by \fBprintf\fR. In this case, any \fBe\fR, \fBn\fR, \fBr\fR, or \fBR\fR options are ignored. Otherwise, unless the \fB-R\fR or \fB-r,\fR are specified, the following escape conventions are applied:
.sp
.ne 2
.mk
.na
\fB\fB\ea\fR\fR
.ad
.RS 8n
.rt  
Alert character (\fBASCII\fR 07)
.RE

.sp
.ne 2
.mk
.na
\fB\fB\eb\fR\fR
.ad
.RS 8n
.rt  
Backspace character (\fBASCII\fR 010)
.RE

.sp
.ne 2
.mk
.na
\fB\fB\ec\fR\fR
.ad
.RS 8n
.rt  
Causes print to end without processing more arguments and not adding a NEWLINE
.RE

.sp
.ne 2
.mk
.na
\fB\fB\ef\fR\fR
.ad
.RS 8n
.rt  
Form-feed character (\fBASCII\fR 014)
.RE

.sp
.ne 2
.mk
.na
\fB\fB\en\fR\fR
.ad
.RS 8n
.rt  
NEWLINE character (\fBASCII\fR 012)
.RE

.sp
.ne 2
.mk
.na
\fB\fB\er\fR\fR
.ad
.RS 8n
.rt  
RETURN character (\fBASCII\fR 015)
.RE

.sp
.ne 2
.mk
.na
\fB\fB\et\fR\fR
.ad
.RS 8n
.rt  
TAB character (\fBASCII\fR 011)
.RE

.sp
.ne 2
.mk
.na
\fB\fB\ev\fR\fR
.ad
.RS 8n
.rt  
Vertical TAB character (\fBASCII\fR 013)
.RE

.sp
.ne 2
.mk
.na
\fB\fB\eE\fR\fR
.ad
.RS 8n
.rt  
Escape character (\fBASCII\fR 033)
.RE

.sp
.ne 2
.mk
.na
\fB\fB\e\e\fR\fR
.ad
.RS 8n
.rt  
Backslash character \fB\e\fR
.RE

.sp
.ne 2
.mk
.na
\fB\fB\e0\fR\fIx\fR\fR
.ad
.RS 8n
.rt  
Character defined by the 1, 2, or 3-digit octal string specified by \fIx\fR
.RE

The \fB-R\fR option prints all subsequent arguments and options other than \fB-n\fR. The \fB-e\fR causes the escape conventions to be applied This is the default behavior. It reverses the effect of an earlier \fB-r\fR. The \fB-p\fR option causes the arguments to be written onto the pipe of the process spawned with \fB|&\fR instead of standard output. The \fB-s\fR option causes the arguments to be written onto the history file instead of standard output. The \fB-u\fR option can be used to specify a one digit file descriptor unit number \fIunit\fR on which the output is placed. The default is \fB1\fR. If the option \fB-n\fR is used, no NEWLINE is added to the output.
.RE

.sp
.ne 2
.mk
.na
\fB\fBprintf\fR \fIformat\fR\fB[\fR\fIarg ...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
The arguments \fIarg\fR are printed on standard output in accordance with the \fBANSI-C\fR formatting rules associated with the format string \fIformat\fR. If the number of arguments exceeds the number of format specifications, the format string is reused to format remaining arguments. The following extensions can also be used: A \fB%b\fR format can be used instead of \fB%s\fR to cause escape sequences in the corresponding \fIarg\fR to be expanded as described in \fBprint\fR. A \fB%B\fR option causes each of the arguments to be treated as variable names and the binary value of the variables is printed. This is most useful for variables with an attribute of b. A \fB%H\fR format can be used instead of \fB%s\fR to cause characters in \fIarg\fR that are special in \fBHTML\fR and \fBXML\fR to be output as their entity name. A \fB%P\fR format can be used instead of \fB%s\fR to cause \fIarg\fR to be interpreted as an extended regular expression and be printed as a shell pattern. A \fB%R\fR format can be used instead of \fB%s\fR to cause \fIarg\fR to be interpreted as a shell pattern and to be printed as an extended regular expression. A \fB%q\fR format can be used instead of \fB%\fRs to cause the resulting string to be quoted in a manner than can be input again to the shell. A \fB%(\fR\fIdate-format\fR\fB)T\fR format can be use to treat an argument as a date/time string and to format the date/time according to the \fIdate-format\fR as defined for the \fBdate\fR(1) command. A \fB%Z\fR format outputs a byte whose value is 0. The precision field of the %d format can be followed by a . and the output base. In this case, the \fB#\fR flag character causes \fBbase\fR\fI#\fR to be prepended. The \fB#\fR flag when used with the \fBd\fR specifier without an output base, causes the output to be displayed in thousands units with one of the suffixes \fBk\fR \fBM\fR \fBG\fR \fBT\fR \fBP\fR \fBE\fR to indicate the unit. The \fB#\fR flag when used with the i specifier causes the output to be displayed in \fB1024\fR with one of the suffixes \fBKi\fR \fBMi\fR \fBGi\fR \fBTi\fR \fBPi\fR \fBEi\fR to indicate the unit. The \fB=\fR flag has been added to center the output within the specified field width.
.RE

.sp
.ne 2
.mk
.na
\fB\fBpwd\fR [\fB-LP\fR]\fR
.ad
.sp .6
.RS 4n
Outputs the value of the current working directory. The \fB-L\fR option is the default. It prints the logical name of the current directory. If the \fB-P\fR option is specified, all symbolic links are resolved from the name. The last instance of \fB-L\fR or \fB-P\fR on the command line determines which method is used.
.RE

.sp
.ne 2
.mk
.na
\fB\fBread\fR \fB[\fR\fB-Aprs\fR\fB] [\fR\fB-d\fR \fIdelim\fR\fB] [\fR \fB-n\fR \fIn\fR\fB] [[\fR \fB-N\fR \fIn\fR\fB] [[\fR\fB-t\fR \fItimeout\fR\fB] [\fR\fB-u\fR \fIunit\fR\fB] [\fR\fIvname\fR\fB?\fR\fIprompt\fR\fB] [\fR \fIvname ...\fR \fB]\fR\fR
.ad
.sp .6
.RS 4n
The shell input mechanism. One line is read and is broken up into fields using the characters in IFS as separators. The escape character, \fB\e\fR, is used to remove any special meaning for the next character and for line continuation. The \fB-d\fR option causes the read to continue to the first character of \fIdelim\fR rather than \fBNEWLINE\fR. The \fB-n\fR option causes at most \fIn\fR bytes to read rather a full line but returns when reading from a slow device as soon as any characters have been read. The \fB-N\fR option causes exactly \fIn\fR to be read unless an end-of-file has been encountered or the read times out because of the \fB-t\fR option. In raw mode, \fB-r\fR, the \fB\e\fR character is not treated specially. The first field is assigned to the first \fIvname\fR, the second field to the second \fIvname\fR, etc., with leftover fields assigned to the last \fIvname\fR. When \fIvname\fR has the binary attribute and \fB-n\fR or \fB-N\fR is specified, the bytes that are read are stored directly into the variable. If the -v is specified, then the value of the first \fIvname\fR is used as a default value when reading from a terminal device. The \fB-A\fR option causes the variable \fIvname\fR to be unset and each field that is read to be stored in successive elements of the indexed array \fIvname\fR. The \fB-p\fR option causes the input line to be taken from the input pipe of a process spawned by the shell using \fB|&\fR. If the \fB-s\fR option is present, the input is saved as a command in the history file. The option \fB-u\fR can be used to specify a one digit file descriptor unit \fIunit\fR to read from. The file descriptor can be opened with the \fBexec\fR special built-in command. The default value of unit \fIn\fR is \fB0\fR. The option \fB-t\fR is used to specify a time out in seconds when reading from a terminal or pipe. If \fIvname\fR is omitted, then REPLY is used as the default \fIvname\fR. An end-of-file with the \fB-p\fR option causes cleanup for this process so that another can be spawned. If the first argument contains a \fB?\fR, the remainder of this word is used as a prompt on standard error when the shell is interactive. The exit status is \fB0\fR unless an end-of-file is encountered or read has timed out.
.RE

.sp
.ne 2
.mk
.na
\fB\fB++readonly\fR \fB[\fR\fB-p\fR\fB] [\fR \fIvname\fR\fB[=\fR\fIvalue\fR\fB]] ...\fR\fR
.ad
.sp .6
.RS 4n
If \fIvname\fR is not specified, the names and values of each variable with the read-only attribute is printed with the values quoted in a manner that allows them to be input again. The \fB-p\fR option causes the word \fBreadonly\fR to be inserted before each one. Otherwise, the specified \fIvname\fRs are marked \fBreadonly\fR and these names cannot be changed by subsequent assignment. 
.RE

.sp
.ne 2
.mk
.na
\fB\fB+return\fR \fB[\fR\fIn\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Causes a shell function or script to return to the invoking script with the exit status specified by \fIn\fR. The value is the least significant 8 bits of the specified status. If \fBn\fR is omitted, then the return status is that of the last command executed. If return is invoked while not in a function or a script, then it behaves the same as exit. 
.RE

.sp
.ne 2
.mk
.na
\fB\fB+set [ \(+-BCGabefhkmnoprstuvx] [\(+-o [\fR \fIoption\fR \fB] ] ... [ \(+-A\fR \fIvname\fR\fB]\fR \fB[\fR\fIarg...\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
The \fBset\fR command supports the following options:
.sp
.ne 2
.mk
.na
\fB\fB-a\fR\fR
.ad
.sp .6
.RS 4n
All subsequent variables that are defined are automatically exported.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-A\fR\fR
.ad
.sp .6
.RS 4n
Array assignment. Unset the variable \fIvname\fR and assign values sequentially from the \fIarg\fR list. If \fB+A\fR is used, the variable \fIvname\fR is not unset first.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-b\fR\fR
.ad
.sp .6
.RS 4n
Prints job completion messages as soon as a background job changes state rather than waiting for the next prompt.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-B\fR\fR
.ad
.sp .6
.RS 4n
Enable brace pattern field generation. This is the default behavior.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-C\fR\fR
.ad
.sp .6
.RS 4n
Prevents redirection (\fB>\fR) from truncating existing files. Files that are created are opened with the \fBO_EXCL\fR mode. Requires \fB>|\fR to truncate a file when turned on.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-e\fR\fR
.ad
.sp .6
.RS 4n
If a command has a \fBnon-zero\fR exit status, execute the \fBERR\fR trap, if set, and exit. This mode is disabled while reading profiles.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-f\fR\fR
.ad
.sp .6
.RS 4n
Disables file name generation.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-G\fR\fR
.ad
.sp .6
.RS 4n
Causes the pattern \fB**\fR by itself to match files and zero or more directories and subdirectories when used for file name generation. If followed by a \fB/\fR only directories and subdirectories are matched.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-h\fR\fR
.ad
.sp .6
.RS 4n
Each command becomes a tracked alias when first encountered.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-k\fR\fR
.ad
.sp .6
.RS 4n
Obsolete. All variable assignment arguments are placed in the environment for a command, not just those that precede the command name.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-m\fR\fR
.ad
.sp .6
.RS 4n
Background jobs run in a separate process group and a line prints upon completion. The exit status of background jobs is reported in a completion message. On systems with job control, this option is turned on automatically for interactive shells.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-n\fR\fR
.ad
.sp .6
.RS 4n
Read commands and check them for syntax errors, but do not execute them. Ignored for interactive shells.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-o\fR\fR
.ad
.sp .6
.RS 4n
If no option name is supplied, the list of options and their current settings are written to standard output. When invoked with a \fB+\fR, the options are written in a format that can be input again to the shell to restore the settings. This option can be repeated to enable or disable multiple options.
.sp
The following argument can be one of the following option names:
.sp
.ne 2
.mk
.na
\fB\fBallexport\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-a\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBbgnice\fR\fR
.ad
.sp .6
.RS 4n
All background jobs are run at a lower priority. This is the default mode.
.RE

.sp
.ne 2
.mk
.na
\fB\fBbraceexpand\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-\fRB.
.RE

.sp
.ne 2
.mk
.na
\fB\fBemacs\fR\fR
.ad
.sp .6
.RS 4n
Puts you in an \fBemacs\fR style inline editor for command entry.
.RE

.sp
.ne 2
.mk
.na
\fB\fBerrexit\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-e\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBglobstar\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-G\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBgmacs\fR\fR
.ad
.sp .6
.RS 4n
Puts you in a \fBgmacs\fR style inline editor for command entry.
.RE

.sp
.ne 2
.mk
.na
\fB\fBignoreeof\fR\fR
.ad
.sp .6
.RS 4n
The shell does not exit on end-of-file. The command \fBexit\fR must be used.
.RE

.sp
.ne 2
.mk
.na
\fB\fBkeyword\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-k\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBmarkdirs\fR\fR
.ad
.sp .6
.RS 4n
All directory names resulting from file name generation have a trailing / appended.
.RE

.sp
.ne 2
.mk
.na
\fB\fBmonitor\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-m\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBmultiline\fR\fR
.ad
.sp .6
.RS 4n
The built-in editors use multiple lines on the screen for lines that are longer than the width of the screen. This might not work for all terminals.
.RE

.sp
.ne 2
.mk
.na
\fB\fBnoclobber\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-C\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBnoexec\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-n\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBnoglob\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-f\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBnolog\fR\fR
.ad
.sp .6
.RS 4n
Do not save function definitions in the history file.
.RE

.sp
.ne 2
.mk
.na
\fB\fBnotify\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-b\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBnounset\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-u\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBpipefail\fR\fR
.ad
.sp .6
.RS 4n
A pipeline does not complete until all components of the pipeline have completed, and the return value is the value of the last \fBnon-zero\fR command to fail or zero if no command has failed.
.RE

.sp
.ne 2
.mk
.na
\fB\fBprivileged\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-p\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBshowme\fR\fR
.ad
.sp .6
.RS 4n
When enabled, simple commands or pipelines preceded by a a semicolon (\fB;\fR) is displayed as if the \fBxtrace\fR option were enabled but is not executed. Otherwise, the leading \fB;\fR is ignored.
.RE

.sp
.ne 2
.mk
.na
\fB\fBtrackall\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-h\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBverbose\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-v\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBvi\fR\fR
.ad
.sp .6
.RS 4n
Puts you in insert mode of a \fBvi\fR style inline editor until you hit the escape character 033. This puts you in control mode. A return sends the line.
.RE

.sp
.ne 2
.mk
.na
\fB\fBviraw\fR\fR
.ad
.sp .6
.RS 4n
Each character is processed as it is typed in \fBvi\fR mode.
.RE

.sp
.ne 2
.mk
.na
\fB\fBxtrace\fR\fR
.ad
.sp .6
.RS 4n
Same as \fB-x\fR. 
.sp
If no option name is supplied, the current options settings are printed.
.RE

.RE

.sp
.ne 2
.mk
.na
\fB\fB-p\fR\fR
.ad
.sp .6
.RS 4n
Disables processing of the \fB$HOME/.profile\fR file and uses the file \fB/etc/suid_profile\fR instead of the \fBENV\fR file. This mode is on whenever the effective \fBuid\fR (\fBgid\fR) is not equal to the real \fBuid\fR (\fBgid\fR). Turning this off causes the effective \fBuid\fR and \fBgid\fR to be set to the real \fBuid\fR and \fBgid\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-r\fR\fR
.ad
.sp .6
.RS 4n
Enables the restricted shell. This option cannot be unset once set.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-s\fR\fR
.ad
.sp .6
.RS 4n
Sort the positional parameters lexicographically.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-t\fR\fR
.ad
.sp .6
.RS 4n
Obsolete. Exit after reading and executing one command.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-u\fR\fR
.ad
.sp .6
.RS 4n
Treat \fBunset\fR parameters as an error when substituting.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-v\fR\fR
.ad
.sp .6
.RS 4n
Print shell input lines as they are read.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-x\fR\fR
.ad
.sp .6
.RS 4n
Print commands and their arguments as they are executed.
.RE

.sp
.ne 2
.mk
.na
\fB\fB--\fR\fR
.ad
.sp .6
.RS 4n
Do not change any of the options. This is useful in setting \fB$1\fR to a value beginning with \fB-\fR. If no arguments follow this option then the positional parameters are unset.
.RE

As an obsolete feature, if the first \fIarg\fR is - then the \fB-x\fR and \fB-v\fR options are turned off and the next \fIarg\fR is treated as the first argument. Using \fB+\fR rather than \fB-\fR causes these options to be turned off. These options can also be used upon invocation of the shell. The current set of options can be found in \fB$-\fR. Unless \fB-A\fR is specified, the remaining arguments are positional parameters and are assigned, in order, to \fB$1 $2 \&....\fR If no arguments are specified, then the names and values of all variables are printed on the standard output.
.RE

.sp
.ne 2
.mk
.na
\fB\fB+shift\fR \fB[\fR\fIn\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
The positional parameters from \fB$\fR\fIn\fR\fB+1 ...\fR are renamed \fB$1 ...\fR, the default \fIn\fR is \fB1\fR. The parameter \fIn\fR can be any arithmetic expression that evaluates to a non-negative number less than or equal to \fB$#\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB+trap\fR \fB-p\fR \fB[\fR\fIaction\fR\fB]\fR \fB[\fR\fIsig\fR\fB] ...\fR\fR
.ad
.sp .6
.RS 4n
The \fB-p\fR option causes the trap action associated with each trap as specified by the arguments to be printed with appropriate quoting. Otherwise, \fIaction\fR is processed as if it were an argument to \fBeval\fR when the shell receives signal(s) \fIsig\fR. Each \fIsig\fR can be specified as a number or as the name of the signal. Trap commands are executed in order of signal number. Any attempt to set a trap on a signal that was ignored on entry to the current shell is ineffective. If \fIaction\fR is omitted and the first \fIsig\fR is a number, or if \fIaction\fR is \fB-\fR, then the trap(s) for each \fIsig\fR are reset to their original values. If \fIaction\fR is the null string then this signal is ignored by the shell and by the commands it invokes. If \fIsig\fR is \fBERR\fR then \fIaction\fR is executed whenever a command has a \fBnon-zero\fR exit status. If \fIsig\fR is \fBDEBUG\fR then \fIaction\fR is executed before each command. The variable \fB\&.sh.command\fR contains the contents of the current command line when \fIaction\fR is running. If \fIsig\fR is \fB0\fR or \fBEXIT\fR and the trap statement is executed inside the body of a function defined with the \fBfunction\fR \fIname\fR syntax, then the command \fIaction\fR is executed after the function completes. If \fIsig\fR is \fB0\fR or \fBEXIT\fR for a trap set outside any function then the command \fIaction\fR is executed on exit from the shell. If \fIsig\fR is \fBKEYBD\fR, then \fIaction\fR is executed whenever a key is read while in \fBemacs\fR, \fBgmacs\fR, or \fBvi\fR mode. The \fBtrap\fR command with no arguments prints a list of commands associated with each signal number.
.RE

.sp
.ne 2
.mk
.na
\fB\fBtrue\fR\fR
.ad
.sp .6
.RS 4n
Does nothing, and exits \fB0\fR. Used with while for infinite loops.
.RE

.sp
.ne 2
.mk
.na
\fB\fB++typeset [\(+-AHflabnprtux ] [ \(+-EFLRZi[\fR\fIn\fR\fB] ] [\fR \fIvname\fR\fB[=\fR\fIvalue\fR \fB] ]\fR\fR
.ad
.sp .6
.RS 4n
Sets attributes and values for shell variables and functions. When invoked inside a function defined with the \fBfunction\fR \fIname\fR syntax, a new instance of the variable \fIvname\fR is created, and the variable's value and type are restored when the function completes. 
.sp
Using \fB+\fR rather than \fB-\fR causes these options to be turned off. If no \fIvname\fR arguments are specified, a list of \fIvname\fRs (and optionally the \fIvalue\fRs) of the variables is printed. Using \fB+\fR rather than \fB-\fR keeps the values from being printed.) The \fB-p\fR option causes \fBtypeset\fR followed by the option letters to be printed before each name rather than the names of the options. If any option other than \fB-p\fR is specified, only those variables which have all of the specified options are printed. Otherwise, the \fIvname\fRs and \fIattributes\fR of all variables that have attributes are printed.
.sp
The following list of attributes can be specified:
.sp
.ne 2
.mk
.na
\fB\fB-a\fR\fR
.ad
.RS 6n
.rt  
Declares \fIvname\fR to be an indexed array. This is optional unless except for compound variable assignments.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-A\fR\fR
.ad
.RS 6n
.rt  
Declares \fIvname\fR to be an associative array. Sub-scripts are strings rather than arithmetic expressions.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-b\fR\fR
.ad
.RS 6n
.rt  
The variable can hold any number of bytes of data. The data can be text or binary. The value is represented by the \fBbase64\fR encoding of the data. If \fB-Z\fR is also specified, the size in bytes of the data in the buffer is determined by the size associated with the \fB-Z\fR. If the \fBbase64\fR string assigned results in more data, it is truncated. Otherwise, it is filled with bytes whose value is zero. The \fBprintf\fR format \fB%B\fR can be used to output the actual data in this buffer instead of the \fBbase64\fR encoding of the data.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-E\fR\fR
.ad
.RS 6n
.rt  
Declares \fIvname\fR to be a double precision floating point number. If \fIn\fR is \fBnon-zero\fR, it defines the number of significant figures that are used when expanding \fIvname\fR. Otherwise, ten significant figures is used.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-f\fR\fR
.ad
.RS 6n
.rt  
The names refer to function names rather than variable names. No assignments can be made and the only other valid options are \fB-t\fR, \fB-u\fR, and \fB-x.\fR The \fB-t\fR option turns on execution tracing for this function. The \fB-u\fR option causes this function to be marked undefined. The \fBFPATH\fR variable is searched to find the function definition when the function is referenced. If no options other than \fB-f\fR is specified, then the function definition is displayed on standard output. If \fB+f\fR is specified, then a line containing the function name followed by a shell comment containing the line number and path name of the file where this function was defined, if any, is displayed.
.sp
The \fB-i\fR attribute cannot be specified with \fB-f\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-F\fR\fR
.ad
.RS 6n
.rt  
Declares \fIvname\fR to be a double precision floating point number. If \fIn\fR is \fBnon-zero\fR, it defines the number of places after the decimal point that are used when expanding \fIvname\fR. Otherwise ten places after the decimal point is used.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-H\fR\fR
.ad
.RS 6n
.rt  
This option provides UNIX to hostname file mapping on non-UNIX machines.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-i\fR\fR
.ad
.RS 6n
.rt  
Declares \fIvname\fR to be represented internally as integer. The right hand side of an assignment is evaluated as an arithmetic expression when assigning to an integer. If \fIn\fR is \fBnon-zero\fR, it defines the output arithmetic base, otherwise the output base is ten.
.sp
The \fB-i\fR attribute cannot be specified along with \fB-R\fR, \fB-L\fR, \fB-Z\fR, or \fB-f\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-l\fR\fR
.ad
.RS 6n
.rt  
All uppercase characters are converted to lowercase. The uppercase option, \fB-u\fR, is turned off.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-L\fR\fR
.ad
.RS 6n
.rt  
Left justify and remove leading blanks from \fIvalue\fR. If \fIn\fR is \fBnon-zero\fR, it defines the width of the field, otherwise it is determined by the width of the value of first assignment. When the variable is assigned to, it is filled on the right with blanks or truncated, if necessary, to fit into the field. The \fB-R\fR option is turned off.
.sp
The \fB-i\fR attribute cannot be specified with \fB-L\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-n\fR\fR
.ad
.RS 6n
.rt  
Declares \fIvname\fR to be a reference to the variable whose name is defined by the value of variable \fIvname\fR. This is usually used to reference a variable inside a function whose name has been passed as an argument.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-R\fR\fR
.ad
.RS 6n
.rt  
Right justify and fill with leading blanks. If \fIn\fR is \fBnon-zero\fR, it defines the width of the field, otherwise it is determined by the width of the value of first assignment. The field is left filled with blanks or truncated from the end if the variable is reassigned. The \fB-L\fR option is turned off.
.sp
The \fB-i\fR attribute cannot be specified with \fB-R\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-r\fR\fR
.ad
.RS 6n
.rt  
The specified \fIvname\fRs are marked read-only and these names cannot be changed by subsequent assignment.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-t\fR\fR
.ad
.RS 6n
.rt  
Tags the variables. Tags are user definable and have no special meaning to the shell.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-u\fR\fR
.ad
.RS 6n
.rt  
All lowercase characters are converted to uppercase. The lowercase option, \fB-l\fR, is turned off.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-x\fR\fR
.ad
.RS 6n
.rt  
The specified \fIvname\fRs are marked for automatic export to the environment of subsequently-executed commands. Variables whose names contain a . cannot be exported.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-Z\fR\fR
.ad
.RS 6n
.rt  
Right justify and fill with leading zeros if the first non-blank character is a digit and the \fB-L\fR option has not been set. Remove leading zeros if the \fB-L\fR option is also set. If \fIn\fR is \fBnon-zero\fR, it defines the width of the field, otherwise it is determined by the width of the value of first assignment.
.sp
The \fB-i\fR attribute cannot be specified with \fB-Z\fR.
.RE

.RE

.sp
.ne 2
.mk
.na
\fB\fBulimit [\fR\fB-HSacdfmnpstv\fR\fB] [\fR \fIlimit\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Set or display a resource limit. Many systems do not support one or more of these limits. The limit for a specified resource is set when \fIlimit\fR is specified. The value of \fIlimit\fR can be a number in the unit specified with each resource, or the value unlimited. When more than one resource is specified, then the limit name and unit is printed before the value.
.sp
If no option is specified, \fB-f\fR is assumed.
.sp
The following are the available resource limits:
.sp
.ne 2
.mk
.na
\fB\fB-a\fR\fR
.ad
.RS 6n
.rt  
Lists all of the current resource limits.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-c\fR\fR
.ad
.RS 6n
.rt  
The number of 512-byte blocks on the size of core dumps.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-d\fR\fR
.ad
.RS 6n
.rt  
The number of Kbytes on the size of the data area.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-f\fR\fR
.ad
.RS 6n
.rt  
The number of 512-byte blocks on files that can be written by the current process or by child processes (files of any size can be read).
.RE

.sp
.ne 2
.mk
.na
\fB\fB-H\fR\fR
.ad
.RS 6n
.rt  
Specifies a hard limit for the specified resource.
.sp
A hard limit cannot be increased once it is set.
.sp
If neither the \fB-H\fR nor \fB-S\fR option is specified, the limit applies to both. The current resource limit is printed when \fIlimit\fR is omitted. In this case, the soft limit is printed unless \fB-H\fR is specified.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-m\fR\fR
.ad
.RS 6n
.rt  
The number of Kbytes on the size of physical memory.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-n\fR\fR
.ad
.RS 6n
.rt  
The number of file descriptors plus 1.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-p\fR\fR
.ad
.RS 6n
.rt  
The number of 512-byte blocks for pipe buffering.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-s\fR\fR
.ad
.RS 6n
.rt  
The number of Kbytes on the size of the stack area.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-S\fR\fR
.ad
.RS 6n
.rt  
Specifies a soft limit for the specified resource.
.sp
A soft limit can be increased up to the value of the hard limit. 
.sp
If neither the \fB-H\fR nor \fB-S\fR option is specified, the limit applies to both. The current resource limit is printed when \fIlimit\fR is omitted. In this case, the soft limit is printed unless \fB-H\fR is specified.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-t\fR\fR
.ad
.RS 6n
.rt  
The number of CPU seconds to be used by each process.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-v\fR\fR
.ad
.RS 6n
.rt  
The number of Kbytes for virtual memory.
.RE

.RE

.sp
.ne 2
.mk
.na
\fB\fBumask\fR \fB[\fR\fB-S\fR\fB]\fR\fB[\fR\fImask\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
The user file-creation mask is set to \fImask\fR. \fImask\fR can either be an octal number or a symbolic value as described in \fBchmod\fR(1). 
.sp
If a symbolic value is specified, the new \fBumask\fR value is the complement of the result of applying \fImask\fR to the complement of the previous \fBumask\fR value. If \fImask\fR is omitted, the current value of the mask is printed. The \fB-S\fR option causes the mode to be printed as a symbolic value. Otherwise, the mask is printed in octal. 
.sp
See \fBumask\fR(2)
.RE

.sp
.ne 2
.mk
.na
\fB\fB+unalias\fR \fB[\fR\fB-a\fR\fB]\fR \fIname\fR\fR
.ad
.sp .6
.RS 4n
The aliases specified by the list of \fIname\fRs are removed from the alias list. The \fB-a\fR option causes all the aliases to be unset.
.RE

.sp
.ne 2
.mk
.na
\fB\fB+unset\fR \fB[\fR\fB-fnv\fR\fB]\fR \fIvname\fR\fR
.ad
.sp .6
.RS 4n
The variables specified by the list of \fIvname\fRs are unassigned, i.e., their values and attributes are erased. Read-only variables cannot be unset. If the \fB-f\fR option is set, then the names refer to function names. If the \fB-v\fR option is set, then the names refer to variable names. The \fB-f\fR option overrides \fB-v\fR. If \fB-n\fR is set and \fIname\fR is a name reference, then \fIname\fR is unset rather than the variable that it references. The default is equivalent to \fB-v\fR. Unsetting \fBLINENO\fR, \fBMAILCHECK\fR, \fBOPTARG\fR, \fBOPTIND\fR, \fBRANDOM\fR, \fBSECONDS\fR, \fBTMOUT\fR, and \fB_\fR removes their special meaning even if they are subsequently assigned to.
.RE

.sp
.ne 2
.mk
.na
\fB\fBwait\fR \fB[\fR\fIjob\fR\fB]\fR\fR
.ad
.sp .6
.RS 4n
Wait for the specified job and report its termination status. If \fIjob\fR is not specified, then all currently active child processes are waited for. The exit status from this command is that of the last process waited for if \fIjob\fR is specified; otherwise it is zero. See \fBJobs\fR for a description of the format of \fIjob\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fBwhence\fR \fB[\fR\fB-afpv\fR\fB]\fR \fIname ...\fR\fR
.ad
.sp .6
.RS 4n
For each \fIname\fR, indicate how it would be interpreted if used as a command name. The \fB-v\fR option produces a more verbose report. The \fB-f\fR option skips the search for functions. The \fB-p\fR option does a path search for \fIname\fR even if name is an alias, a function, or a reserved word. The \fB-a\fR option is similar to the -v option but causes all interpretations of the specified name to be reported.
.RE

.SS "Invocation"
.sp
.LP
If the shell is invoked by \fBexec\fR(2), and the first character of argument zero (\fB$0\fR) is \fB-\fR, then the shell is assumed to be a login shell and commands are read from \fB/etc/profile\fR and then from \fB$HOME/.profile\fR. Next, for interactive shells, commands are read first from \fB/etc/ksh.kshrc\fR, and then from the file named by performing parameter expansion, command substitution, and arithmetic substitution on the value of the environment variable \fBENV\fR if the file exists. If the \fB-s\fR option is not present and \fIarg\fR and a file by the name of \fIarg\fR exists, then it reads and executes this script. Otherwise, if the first \fIarg\fR does not contain a \fB/\fR, a path search is performed on the first \fIarg\fR to determine the name of the script to execute. The script \fIarg\fR must have execute permission and any \fBsetuid\fR and \fBsetgid\fR settings are ignored. If the script is not found on the path, \fIarg\fR is processed as if it named a built-in command or function. 
.sp
.LP
Commands are then read as described, and the following options are interpreted by the shell when it is invoked:
.sp
.ne 2
.mk
.na
\fB\fB-c\fR\fR
.ad
.RS 15n
.rt  
If the \fB-c\fR option is present, then commands are read from the first \fIarg\fR. Any remaining arguments become positional parameters starting at \fB0\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-D\fR\fR
.ad
.RS 15n
.rt  
A list of all double quoted strings that are preceded by a \fB$\fR is printed on standard output and the shell exits. This set of strings is subject to language translation when the locale is not C or POSIX. No commands are executed.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-i\fR\fR
.ad
.RS 15n
.rt  
If the \fB-i\fR option is present or if the shell input and output are attached to a terminal (as told by \fBtcgetattr\fR(3C), this shell is interactive. In this case \fBTERM\fR is ignored (so that \fBkill 0\fR does not kill an interactive shell) and \fBINTR\fR is caught and ignored (so that wait is interruptible). In all cases, \fBQUIT\fR is ignored by the shell.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-R\fR \fIfilename\fR\fR
.ad
.RS 15n
.rt  
The \fB-R\fR \fIfilename\fR option is used to generate a cross reference database that can be used by a separate utility to find definitions and references for variables and commands.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-r\fR\fR
.ad
.RS 15n
.rt  
If the \fB-r\fR option is present, the shell is a restricted shell.
.RE

.sp
.ne 2
.mk
.na
\fB\fB-s\fR\fR
.ad
.RS 15n
.rt  
If the \fB-s\fR option is present or if no arguments remain, then commands are read from the standard input. Shell output, except for the output of the \fBSpecial Commands\fR listed, is written to file descriptor 2.
.RE

.sp
.LP
The remaining options and arguments are described under the \fBset\fR command. An optional \fB-\fR as the first argument is ignored.
.SS "\fBrksh\fR Only"
.sp
.LP
\fBrksh\fR is used to set up login names and execution environments whose capabilities are more controlled than those of the standard shell.
.sp
.LP
The actions of \fBrksh\fR are identical to those of \fBksh\fR, except that the following are disallowed:
.RS +4
.TP
.ie t \(bu
.el o
Unsetting the restricted option
.RE
.RS +4
.TP
.ie t \(bu
.el o
Changing directory. See \fBcd\fR(1).
.RE
.RS +4
.TP
.ie t \(bu
.el o
Setting or unsetting the value or attributes of \fBSHELL\fR, \fBENV\fR, \fBFPATH\fR, or \fBPATH\fR
.RE
.RS +4
.TP
.ie t \(bu
.el o
Specifying path or command names containing \fB/\fR,
.RE
.RS +4
.TP
.ie t \(bu
.el o
Redirecting output (\fB>\fR, \fB>\fR\fB|\fR, \fB<>\fR, and \fB>>\fR).
.RE
.RS +4
.TP
.ie t \(bu
.el o
Adding or deleting built-in commands.
.RE
.RS +4
.TP
.ie t \(bu
.el o
Using \fBcommand\fR \fB-p\fR to invoke a command.
.RE
.sp
.LP
These restrictions are enforced after .\fBprofile\fR and the \fBENV\fR files are interpreted.
.sp
.LP
When a command to be executed is found to be a shell procedure, \fBrksh\fR invokes \fBksh\fR to execute it. Thus, it is possible to provide to the end-user shell procedures that have access to the full power of the standard shell, while imposing a limited menu of commands. This scheme assumes that the end-user does not have write and execute permissions in the same directory. The net effect of these rules is that the writer of the .\fBprofile\fR has complete control over user actions, by performing guaranteed setup actions and leaving the user in an appropriate directory (probably not the login directory). The system administrator often sets up a directory of commands, for example, \fB/usr/rbin\fR, that can be safely invoked by \fBrksh\fR. 
.SH USAGE
.sp
.LP
See \fBlargefile\fR(5) for the description of the behavior of \fBksh\fR and \fBrksh\fR when encountering files greater than or equal to 2 Gbyte (2^31 bytes).
.SH EXIT STATUS
.sp
.LP
The following exit values are returned:
.sp
.ne 2
.mk
.na
\fB\fBnon-zero\fR\fR
.ad
.sp .6
.RS 4n
Returns \fBnon-zero\fR when errors, such as syntax errors, are detected by the shell.
.sp
If the shell is being used non-interactively, then execution of the shell file is abandoned unless the error occurs inside a sub-shell in which case the sub-shell is abandoned.
.RE

.sp
.ne 2
.mk
.na
\fB\fIexit status of last command executed\fR\fR
.ad
.sp .6
.RS 4n
Returns the exit status of the last command executed.
.sp
Run time errors detected by the shell are reported by printing the command or function name and the error condition. If the line number that the error occurred on is greater than one, then the line number is also printed in square brackets (\fB[]\fR) after the command or function name.
.sp
See the \fBksh exit\fR command for additional details.
.RE

.SH FILES
.sp
.ne 2
.mk
.na
\fB\fB/etc/profile\fR\fR
.ad
.sp .6
.RS 4n
The system initialization file, executed for login shells.
.RE

.sp
.ne 2
.mk
.na
\fB\fB/etc/ksh.kshrc\fR\fR
.ad
.sp .6
.RS 4n
The system wide startup file, executed for interactive shells.
.RE

.sp
.ne 2
.mk
.na
\fB\fB$HOME/.profile\fR\fR
.ad
.sp .6
.RS 4n
The personal initialization file, executed for login shells after \fB/etc/profile\fR.
.RE

.sp
.ne 2
.mk
.na
\fB\fB$HOME/.kshrc\fR\fR
.ad
.sp .6
.RS 4n
Default personal initialization file, executed after \fB/etc/ksh.kshrc\fR, for interactive shells when \fBENV\fR is not set.
.RE

.sp
.ne 2
.mk
.na
\fB\fB/etc/suid-profile\fR\fR
.ad
.sp .6
.RS 4n
Alternative initialization file, executed instead of the personal initialization file when the real and effective user or group id do not match.
.RE

.sp
.ne 2
.mk
.na
\fB\fB/dev/null\fR\fR
.ad
.sp .6
.RS 4n
NULL device.
.RE

.SH AUTHORS
.sp
.LP
David Korn, \fBdgk@research.att.com\fR
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
tab() box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPEATTRIBUTE VALUE
_
Availabilityshell/ksh
_
Interface StabilitySee below.
.TE

.sp
.LP
The scripting interface is Uncommitted. The environment variables, \fB\&.paths\fR feature, and editing modes are Volatile.
.SH SEE ALSO
.sp
.LP
\fBcat\fR(1), \fBcd\fR(1), \fBchmod\fR(1), \fBcut\fR(1), \fBdate\fR(1), \fBegrep\fR(1), \fBecho\fR(1), \fBegrep\fR(1), \fBenv\fR(1), \fBfgrep\fR(1), \fBgrep\fR(1), \fBlogin\fR(1), \fBnewgrp\fR(1), \fBpaste\fR(1), \fBprintf\fR(1), \fBshell_builtins\fR(1), \fBstty\fR(1), \fBtest\fR(1), \fBumask\fR(1), \fBvi\fR(1), \fBdup\fR(2), \fBexec\fR(2), \fBfork\fR(2), \fBioctl\fR(2), \fBlseek\fR(2), \fBpathconf\fR(2), \fBpipe\fR(2), \fBsysconf\fR(3C), \fBulimit\fR(2), \fBumask\fR(2), \fBrand\fR(3C), \fBtcgetattr\fR(3C), \fBwait\fR(3C), \fBa.out\fR(4), \fBprofile\fR(4), \fBattributes\fR(5), \fBenviron\fR(5), \fBlargefile\fR(5), \fBstandards\fR(5)
.sp
.LP
Bolsky, Morris I. and Korn, David G., \fIThe New KornShell Command and Programming Language\fR, Prentice Hall, 1995.
.sp
.LP
\fIPOSIX-Part 2: Shell and Utilities, IEEE Std 1003.2-1992, ISO/IEC 9945-2\fR, IEEE, 1993.
.SH NOTES
.sp
.LP
\fBksh\fR scripts should choose shell function names outside the namespace used by reserved keywords of the ISO C99, C++ and JAVA languages to avoid collisions with future enhancements to \fBksh\fR.
.sp
.LP
If a command is executed, and then a command with the same name is installed in a directory in the search path before the directory where the original command was found, the shell continues to \fBexec\fR the original command. Use the \fB-t\fR option of the alias command to correct this situation.
.sp
.LP
Some very old shell scripts contain a caret (\fB^\fR) as a synonym for the pipe character (\fB|\fR).
.sp
.LP
Using the \fBhist\fR built-in command within a compound command causes the whole command to disappear from the history file.
.sp
.LP
The built-in command \fB\&.\fR \fIfile\fR reads the whole file before any commands are executed. \fBalias\fR and \fBunalias\fR commands in the file do not apply to any commands defined in the file.
.sp
.LP
Traps are not processed while a job is waiting for a foreground process. Thus, a trap on \fBCHLD\fR is not executed until the foreground job terminates.
.sp
.LP
It is a good idea to leave a space after the comma operator in arithmetic expressions to prevent the comma from being interpreted as the decimal point character in certain locales. 
.sp
.LP
There might be some restrictions on creating a \fB\&.paths\fR file which is portable across other operating systems.
.sp
.LP
If the system supports the 64-bit instruction set, \fB/bin/ksh\fR executes the 64-bit version of \fBksh\fR.
